From 69600824d25936fa2bbe2a0b4343cb4cf955b025 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 10:03:49 +0100
Subject: [PATCH 01/13] Refactor Graph tests

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 tests/unit/model/graphs/test_graph_model.py | 435 +++++++++-----------
 1 file changed, 190 insertions(+), 245 deletions(-)

diff --git a/tests/unit/model/graphs/test_graph_model.py b/tests/unit/model/graphs/test_graph_model.py
index 628c77b..e4fe0db 100644
--- a/tests/unit/model/graphs/test_graph_model.py
+++ b/tests/unit/model/graphs/test_graph_model.py
@@ -1,282 +1,208 @@
 # SPDX-FileCopyrightText: Contributors to the Power Grid Model project <powergridmodel@lfenergy.org>
 #
 # SPDX-License-Identifier: MPL-2.0
-
-"""Grid tests"""
-
 import numpy as np
 import pytest
 from numpy.testing import assert_array_equal
 
-from power_grid_model_ds._core.model.graphs.errors import MissingBranchError, MissingNodeError, NoPathBetweenNodes
+from power_grid_model_ds.errors import MissingBranchError, MissingNodeError, NoPathBetweenNodes
 
 # pylint: disable=missing-function-docstring,missing-class-docstring
 
 
-def test_graph_initialize(graph):
-    """We test whether we can make a simple graph of 2 nodes and 1 branch"""
-    graph.add_node(1)
-    graph.add_node(2)
-    graph.add_branch(1, 2)
-
-    # both nodes exist in the external2graph mapping
-    assert 1 in graph.external_ids
-    assert 2 in graph.external_ids
-    # the graph has the correct size
-    assert 2 == graph.nr_nodes
-    assert 1 == graph.nr_branches
-
-
-def test_graph_has_branch(graph):
-    graph.add_node(1)
-    graph.add_node(2)
-    graph.add_branch(1, 2)
-
-    assert graph.has_branch(1, 2)
-    assert graph.has_branch(2, 1)  # reversed should work too
-    assert not graph.has_branch(1, 3)
-
-
-def test_graph_delete_branch(graph):
-    """Test whether a branch is deleted correctly"""
-    graph.add_node(1)
-    graph.add_node(2)
-    graph.add_branch(1, 2)
-    graph.add_node(3)
-
-    assert graph.has_branch(1, 2)
-
-    assert 0 == graph.external_to_internal(1)
-    assert 1 == graph.external_to_internal(2)
-    assert 2 == graph.external_to_internal(3)
-
-    assert 3 == graph.nr_nodes
-    assert 1 == graph.nr_branches
-    assert 1 in graph.external_ids
-    assert 2 in graph.external_ids
-
-    # now delete the 1 -> 2 branch
-    graph.delete_branch(1, 2)
-    assert not graph.has_branch(1, 2)
-
-    assert 0 == graph.external_to_internal(1)
-    assert 1 == graph.external_to_internal(2)
-    assert 2 == graph.external_to_internal(3)
-
-    # check the graph size
-    assert 3 == graph.nr_nodes
-    assert 0 == graph.nr_branches
-    assert 1 in graph.external_ids
-    assert 2 in graph.external_ids
-
-
-def test_graph_add_branch(graph):
-    """Test whether a branch is deleted correctly"""
-    graph.add_node(1)
-    graph.add_node(2)
-    graph.add_branch(1, 2)
-    assert graph.has_branch(1, 2)
-
-    with pytest.raises(MissingNodeError):
-        graph.add_branch(1, 3)
-
-
-def test_has_node(graph):
-    graph.add_node(1)
-    assert graph.has_node(1)
-    assert not graph.has_node(2)
-
-
-# pylint: disable=protected-access
-def test_graph_mapping_of_ids_after_delete_node(graph):
-    """Test whether the node mapping stays correct after deleting a node"""
-    graph.add_node(1)
-    graph.add_node(2)
-    graph.add_node(3)
-
-    internal_id_0 = graph.external_to_internal(1)
-    internal_id_1 = graph.external_to_internal(2)
-    internal_id_2 = graph.external_to_internal(3)
-    assert graph._has_node(internal_id_0)
-    assert graph._has_node(internal_id_1)
-    assert graph._has_node(internal_id_2)
-
-    # now delete node 2, this can change the internal mapping
-    graph.delete_node(2)
-
-    internal_id_0 = graph.external_to_internal(1)
-    internal_id_2 = graph.external_to_internal(3)
-
-    assert graph._has_node(internal_id_0)
-    assert graph._has_node(internal_id_2)
-
-
-def test_graph_delete_node(graph):
-    """Test whether a node is deleted correctly"""
-    graph.add_node(1)
-    graph.add_node(2)
-    graph.add_branch(1, 2)
-
-    # now delete the 1 -> 2 branch
-    graph.delete_node(1)
-
-    # check the graph size, the branch to 1 is also removed!
-    assert 1 == graph.nr_nodes
-    assert 0 == graph.nr_branches
-    # check whether the edge is removed from the graph
-    assert 2 in graph.external_ids
-    assert 1 not in graph.external_ids
-
-    assert not graph.has_branch(1, 2)
-
-
-def test_remove_invalid_node_raises_error(graph):
-    """Test whether an error is raised when nodes are removed incorrectly"""
-    graph.add_node(1)
-    graph.add_node(2)
-
-    # removing non existent nodes and branches raises a error by default
-    with pytest.raises(MissingNodeError):
-        graph.delete_node(3)
-
-    with pytest.raises(MissingBranchError):
-        graph.delete_branch(1, 3)
-
-    with pytest.raises(MissingBranchError):
-        graph.delete_branch(1, 2)
-
+class TestGraphModifications:
+    def test_graph_add_node_and_branch(self, graph):
+        graph.add_node(1)
+        graph.add_node(2)
+        graph.add_branch(1, 2)
 
-def test_remove_invalid_node_without_error(graph):
-    graph.delete_node(3, raise_on_fail=False)
-    graph.delete_branch(1, 3, raise_on_fail=False)
+        # both nodes exist in the external2graph mapping
+        assert 1 in graph.external_ids
+        assert 2 in graph.external_ids
+        # the graph has the correct size
+        assert 2 == graph.nr_nodes
+        assert 1 == graph.nr_branches
 
+    def test_has_node(self, graph):
+        graph.add_node(1)
+        assert graph.has_node(1)
+        assert not graph.has_node(2)
 
-def test_shortest_path(graph_with_5_nodes):
-    """Test shortest path algorithm on circular network"""
-    graph_with_5_nodes.add_branch(1, 2)
-    graph_with_5_nodes.add_branch(2, 3)
+    def test_has_branch(self, graph):
+        graph.add_node(1)
+        graph.add_node(2)
+        graph.add_branch(1, 2)
 
-    path, length = graph_with_5_nodes.get_shortest_path(1, 3)
+        assert graph.has_branch(1, 2)
+        assert graph.has_branch(2, 1)  # reversed should work too
+        assert not graph.has_branch(1, 3)
 
-    assert path == [1, 2, 3]
-    assert length == 2
+    def test_add_invalid_branch(self, graph):
+        graph.add_node(1)
+        graph.add_node(2)
+        graph.add_branch(1, 2)
+        assert graph.has_branch(1, 2)
 
-    path, length = graph_with_5_nodes.get_shortest_path(1, 1)
-    assert path == [1]
-    assert length == 0
+        with pytest.raises(MissingNodeError):
+            graph.add_branch(1, 3)
 
+    def test_delete_invalid_node_without_error(self, graph):
+        graph.delete_node(3, raise_on_fail=False)
 
-def test_shortest_path_no_path(graph_with_5_nodes):
-    """Test that shortest path algorithm raises an error
-    when path between two nodes does not exist"""
-    graph_with_5_nodes.add_branch(1, 2)
-    graph_with_5_nodes.add_branch(3, 4)
-    graph_with_5_nodes.add_branch(4, 5)
+    def test_delete_invalid_branch_without_error(self, graph):
+        graph.delete_branch(1, 3, raise_on_fail=False)
 
-    with pytest.raises(NoPathBetweenNodes):
-        graph_with_5_nodes.get_shortest_path(1, 5)
+    def test_graph_delete_connected_node(self, graph):
+        graph.add_node(1)
+        graph.add_node(2)
+        graph.add_branch(1, 2)
 
+        graph.delete_node(1)  # also deletes branch 1-2
 
-def test_all_paths(graph_with_5_nodes):
-    """Test all paths algorithm on circular network"""
-    graph_with_5_nodes.add_branch(1, 2)
-    graph_with_5_nodes.add_branch(2, 3)
-    graph_with_5_nodes.add_branch(3, 4)
-    graph_with_5_nodes.add_branch(4, 5)
-    graph_with_5_nodes.add_branch(5, 1)
+        assert 1 == graph.nr_nodes
+        assert 0 == graph.nr_branches
+        assert 2 in graph.external_ids
+        assert 1 not in graph.external_ids
+        assert not graph.has_branch(1, 2)
 
-    paths = graph_with_5_nodes.get_all_paths(1, 3)
+    def test_remove_invalid_node(self, graph):
+        graph.add_node(1)
+        graph.add_node(2)
 
-    assert len(paths) == 2
-    assert [1, 2, 3] in paths
-    assert [1, 5, 4, 3] in paths
+        with pytest.raises(MissingNodeError):
+            graph.delete_node(3)
 
+    def test_remove_invalid_branch(self, graph):
+        graph.add_node(1)
+        graph.add_node(2)
 
-def test_all_paths_no_path(graph_with_5_nodes):
-    """Test that all paths algorithm raises an error when path between two nodes does not exist"""
-    with pytest.raises(NoPathBetweenNodes):
-        graph_with_5_nodes.get_all_paths(1, 2)
+        with pytest.raises(MissingBranchError):
+            graph.delete_branch(1, 3)
 
+        with pytest.raises(MissingBranchError):
+            graph.delete_branch(1, 2)
 
-def test_get_components(graph_with_2_routes):
-    """Test whether routes can be correcty extracted"""
-    graph = graph_with_2_routes
-    graph.add_node(99)
-    graph.add_branch(1, 99)
-    substation_nodes = np.array([1])
+    # pylint: disable=protected-access
+    def test_internal_ids_after_node_deletion(self, graph):
+        graph.add_node(1)
+        graph.add_node(2)
+        graph.add_node(3)
 
-    components = graph.get_components(substation_nodes=substation_nodes)
+        internal_id_0 = graph.external_to_internal(1)
+        internal_id_1 = graph.external_to_internal(2)
+        internal_id_2 = graph.external_to_internal(3)
+        assert graph._has_node(internal_id_0)
+        assert graph._has_node(internal_id_1)
+        assert graph._has_node(internal_id_2)
 
-    assert len(components) == 3
-    assert set(components[0]) == {2, 3}
-    assert set(components[1]) == {4, 5}
-    assert set(components[2]) == {99}
+        # now delete node 2, this can change the internal mapping
+        graph.delete_node(2)
 
+        internal_id_0 = graph.external_to_internal(1)
+        internal_id_2 = graph.external_to_internal(3)
 
-def test_from_arrays(basic_grid):
-    new_graph = basic_grid.graphs.complete_graph.__class__.from_arrays(basic_grid)
-    assert_array_equal(new_graph.external_ids, basic_grid.node.id)
+        assert graph._has_node(internal_id_0)
+        assert graph._has_node(internal_id_2)
 
 
-def test_get_shortest_path(graph_with_2_routes):
-    graph = graph_with_2_routes
-    path = graph.get_shortest_path(1, 3)
-    assert path == ([1, 2, 3], 2)
-
-
-@pytest.mark.parametrize(
-    "additional_edges, nodes_in_cycles",
-    [
-        ([], set()),
-        ([(2, 5)], {1, 2, 5}),
-        ([(1, 2)], {1, 2}),
-        ([(1, 2), (1, 2)], {1, 2}),
-        ([(2, 4)], {1, 2, 4, 5}),
-        ([(1, 5), (3, 5)], {1, 2, 3, 5}),
-    ],
-)
-def test_find_nodes_in_cycle(graph_with_2_routes, additional_edges, nodes_in_cycles):
-    graph = graph_with_2_routes
-    for u, v in additional_edges:
-        graph.add_branch(u, v)
-
-    result = graph.find_fundamental_cycles()
-    assert len(result) == len(set(additional_edges))
-    for node_path in result:
-        assert node_path[0] == node_path[-1]
-        assert len(node_path) == len(set(node_path)) + 1
-        assert all(node in nodes_in_cycles for node in node_path)
-
-
-def test_find_nodes_in_cycle_multiple_trees(graph):
-    """The following graph contains 2 unconnected subgraphs of 4 nodes each.
-    Both subgraphs contain a cycle.
-    Visual representation:
-        Subgraph 1:
-            1 -- 2
-            |    |
-            4 -- 3
-        Subgraph 2:
-        5 - 6 -- 7
-            |    |
-            '--- 8
-    """
-    edges = [(1, 2), (2, 3), (3, 4), (1, 4), (5, 6), (6, 7), (6, 8), (7, 8)]
-    for _id in range(1, 9):
-        graph.add_node(_id)
-    for u, v in edges:
-        graph.add_branch(u, v)
-
-    # The MST is not unique, so the node paths can be in any order.
-    # For example: [1,2,3,4,1] and [4,3,2,1,4] are both valid return values.
-    # We do know exactly which nodes are in the cycle and that the first and last node are the same.
-    result = graph.find_fundamental_cycles()
-    result_as_sets = {frozenset(nodes) for nodes in result}
-    assert len(result) == 2
-    assert frozenset([1, 2, 3, 4]) in result_as_sets
-    assert frozenset([6, 7, 8]) in result_as_sets
-    assert result[0][0] == result[0][-1]
-    assert result[1][0] == result[1][-1]
+class TestPathMethods:
+    def test_get_shortest_path(self, graph_with_2_routes):
+        graph = graph_with_2_routes
+        path = graph.get_shortest_path(1, 3)
+        assert path == ([1, 2, 3], 2)
+
+    def test_shortest_path_on_circular_network(self, graph_with_5_nodes):
+        graph_with_5_nodes.add_branch(1, 2)
+        graph_with_5_nodes.add_branch(2, 3)
+
+        path, length = graph_with_5_nodes.get_shortest_path(1, 3)
+
+        assert path == [1, 2, 3]
+        assert length == 2
+
+        path, length = graph_with_5_nodes.get_shortest_path(1, 1)
+        assert path == [1]
+        assert length == 0
+
+    def test_shortest_path_no_path(self, graph_with_5_nodes):
+        graph_with_5_nodes.add_branch(1, 2)
+        graph_with_5_nodes.add_branch(3, 4)
+        graph_with_5_nodes.add_branch(4, 5)
+
+        with pytest.raises(NoPathBetweenNodes):
+            graph_with_5_nodes.get_shortest_path(1, 5)
+
+    def test_all_paths_on_circular_network(self, graph_with_5_nodes):
+        graph_with_5_nodes.add_branch(1, 2)
+        graph_with_5_nodes.add_branch(2, 3)
+        graph_with_5_nodes.add_branch(3, 4)
+        graph_with_5_nodes.add_branch(4, 5)
+        graph_with_5_nodes.add_branch(5, 1)
+
+        paths = graph_with_5_nodes.get_all_paths(1, 3)
+
+        assert len(paths) == 2
+        assert [1, 2, 3] in paths
+        assert [1, 5, 4, 3] in paths
+
+    def test_all_paths_no_path(self, graph_with_5_nodes):
+        with pytest.raises(NoPathBetweenNodes):
+            graph_with_5_nodes.get_all_paths(1, 2)
+
+
+class TestFindFundamentalCycles:
+    @pytest.mark.parametrize(
+        "additional_edges, nodes_in_cycles",
+        [
+            ([], set()),
+            ([(2, 5)], {1, 2, 5}),
+            ([(1, 2)], {1, 2}),
+            ([(1, 2), (1, 2)], {1, 2}),
+            ([(2, 4)], {1, 2, 4, 5}),
+            ([(1, 5), (3, 5)], {1, 2, 3, 5}),
+        ],
+    )
+    def test_find_fundamental_cycles(self, graph_with_2_routes, additional_edges, nodes_in_cycles):
+        graph = graph_with_2_routes
+        for u, v in additional_edges:
+            graph.add_branch(u, v)
+
+        result = graph.find_fundamental_cycles()
+        assert len(result) == len(set(additional_edges))
+        for node_path in result:
+            assert node_path[0] == node_path[-1]
+            assert len(node_path) == len(set(node_path)) + 1
+            assert all(node in nodes_in_cycles for node in node_path)
+
+    def test_find_fundamental_cycles_multiple_trees(self, graph):
+        """The following graph contains 2 unconnected subgraphs of 4 nodes each.
+        Both subgraphs contain a cycle.
+        Visual representation:
+            Subgraph 1:
+                1 -- 2
+                |    |
+                4 -- 3
+            Subgraph 2:
+            5 - 6 -- 7
+                |    |
+                '--- 8
+        """
+        edges = [(1, 2), (2, 3), (3, 4), (1, 4), (5, 6), (6, 7), (6, 8), (7, 8)]
+        for _id in range(1, 9):
+            graph.add_node(_id)
+        for u, v in edges:
+            graph.add_branch(u, v)
+
+        # The MST is not unique, so the node paths can be in any order.
+        # For example: [1,2,3,4,1] and [4,3,2,1,4] are both valid return values.
+        # We do know exactly which nodes are in the cycle and that the first and last node are the same.
+        result = graph.find_fundamental_cycles()
+        result_as_sets = {frozenset(nodes) for nodes in result}
+        assert len(result) == 2
+        assert frozenset([1, 2, 3, 4]) in result_as_sets
+        assert frozenset([6, 7, 8]) in result_as_sets
+        assert result[0][0] == result[0][-1]
+        assert result[1][0] == result[1][-1]
 
 
 class TestGetConnected:
@@ -320,3 +246,22 @@ def test_get_connected_ignore_multiple_nodes(self, graph_with_2_routes):
         connected_nodes = graph.get_connected(node_id=1, nodes_to_ignore=[2, 4])
 
         assert {5} == set(connected_nodes)
+
+
+def test_get_components(graph_with_2_routes):
+    graph = graph_with_2_routes
+    graph.add_node(99)
+    graph.add_branch(1, 99)
+    substation_nodes = np.array([1])
+
+    components = graph.get_components(substation_nodes=substation_nodes)
+
+    assert len(components) == 3
+    assert set(components[0]) == {2, 3}
+    assert set(components[1]) == {4, 5}
+    assert set(components[2]) == {99}
+
+
+def test_from_arrays(basic_grid):
+    new_graph = basic_grid.graphs.complete_graph.__class__.from_arrays(basic_grid)
+    assert_array_equal(new_graph.external_ids, basic_grid.node.id)

From 09595b9d55a13de91cf5234720b7f42153137db8 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 10:41:53 +0100
Subject: [PATCH 02/13] Feature: add Grid.from_txt method

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../_core/model/grids/_text_sources.py        |  16 +--
 .../_core/model/grids/base.py                 |  16 ++-
 tests/unit/model/grids/test_grid_base.py      | 116 +++++++++++-------
 3 files changed, 89 insertions(+), 59 deletions(-)

diff --git a/src/power_grid_model_ds/_core/model/grids/_text_sources.py b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
index c075bde..dc670cb 100644
--- a/src/power_grid_model_ds/_core/model/grids/_text_sources.py
+++ b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
@@ -5,7 +5,6 @@
 """Create a grid from text a text file"""
 
 import logging
-from pathlib import Path
 from typing import TYPE_CHECKING
 
 from power_grid_model_ds._core.model.enums.nodes import NodeType
@@ -35,25 +34,20 @@ class TextSource:
     def __init__(self, grid_class: type["Grid"]):
         self.grid = grid_class.empty()
 
-    def load_grid_from_path(self, path: Path):
-        """Load assets from text file & sort them by id so that
-        they are ready to be appended to the grid"""
-
-        txt_nodes, txt_branches = self.read_txt(path)
+    def load_from_txt(self, txt_lines: list[str]) -> "Grid":
+        """Load a grid from text"""
+        txt_nodes, txt_branches = self.read_txt(txt_lines)
         self.add_nodes(txt_nodes)
         self.add_branches(txt_branches)
         self.grid.set_feeder_ids()
         return self.grid
 
     @staticmethod
-    def read_txt(path: Path) -> tuple[set, dict]:
+    def read_txt(txt_lines: list[str]) -> tuple[set, dict]:
         """Extract assets from text"""
-        with open(path, "r", encoding="utf-8") as f:
-            txt_rows = f.readlines()
-
         txt_nodes = set()
         txt_branches = {}
-        for text_line in txt_rows:
+        for text_line in txt_lines:
             if not text_line.strip() or text_line.startswith("#"):
                 continue  # skip empty lines and comments
             try:
diff --git a/src/power_grid_model_ds/_core/model/grids/base.py b/src/power_grid_model_ds/_core/model/grids/base.py
index 0183ca1..0721f69 100644
--- a/src/power_grid_model_ds/_core/model/grids/base.py
+++ b/src/power_grid_model_ds/_core/model/grids/base.py
@@ -408,6 +408,17 @@ def _from_pickle(cls, pickle_path: Path):
             raise TypeError(f"{pickle_path.name} is not a valid {cls.__name__} cache.")
         return grid
 
+    @classmethod
+    def from_txt(cls, txt_lines: list[str]):
+        """Build a grid from a list of strings
+
+        See the documentation for the expected format of the txt_lines
+
+        Example:
+            >>> Grid.from_txt(["1 2", "2 3", "3 4 transformer", "4 5", "S1 6"])
+        """
+        return TextSource(grid_class=cls).load_from_txt(txt_lines)
+
     @classmethod
     # pylint: disable=arguments-differ
     def from_txt_file(cls, txt_file_path: Path):
@@ -416,8 +427,9 @@ def from_txt_file(cls, txt_file_path: Path):
         Args:
             txt_file_path (Path): The path to the txt file
         """
-        text_source = TextSource(grid_class=cls)
-        return text_source.load_grid_from_path(txt_file_path)
+        with open(txt_file_path, "r", encoding="utf-8") as f:
+            txt_lines = f.readlines()
+        return TextSource(grid_class=cls).load_from_txt(txt_lines)
 
     def set_feeder_ids(self):
         """Sets feeder and substation id properties in the grids arrays"""
diff --git a/tests/unit/model/grids/test_grid_base.py b/tests/unit/model/grids/test_grid_base.py
index 8f9160a..39b68a3 100644
--- a/tests/unit/model/grids/test_grid_base.py
+++ b/tests/unit/model/grids/test_grid_base.py
@@ -266,52 +266,6 @@ def test_grid_make_inactive_to_side(basic_grid):
     assert 0 == target_line_after.to_status
 
 
-def test_from_txt_file(tmp_path):
-    """Test that Grid can be created from txt file"""
-    txt_file = tmp_path / "tmp_grid"
-    txt_file.write_text("S1 2\nS1 3 open\n2 7\n3 5\n3 6 transformer\n5 7\n7 8\n8 9", encoding="utf-8")
-    grid = Grid.from_txt_file(txt_file)
-    txt_file.unlink()
-
-    assert 8 == grid.node.size
-    assert 1 == grid.branches.filter(to_status=0).size
-    assert 1 == grid.transformer.size
-    np.testing.assert_array_equal([14, 10, 11, 12, 13, 15, 16, 17], grid.branches.id)
-
-
-def test_from_txt_file_with_branch_ids(tmp_path):
-    txt_file = tmp_path / "tmp_grid"
-    txt_file.write_text(
-        "S1 2 91\nS1 3 92,open\n2 7 93\n3 5 94\n3 6 transformer,95\n5 7 96\n7 8 97\n8 9 98", encoding="utf-8"
-    )
-    grid = Grid.from_txt_file(txt_file)
-    txt_file.unlink()
-
-    assert 8 == grid.node.size
-    assert 1 == grid.branches.filter(to_status=0).size
-    assert 1 == grid.transformer.size
-    np.testing.assert_array_equal([95, 91, 92, 93, 94, 96, 97, 98], grid.branches.id)
-
-
-def test_from_txt_file_conflicting_ids(tmp_path):
-    txt_file = tmp_path / "tmp_grid"
-    txt_file.write_text("S1 2\n1 3", encoding="utf-8")
-
-    with pytest.raises(ValueError):
-        Grid.from_txt_file(txt_file)
-
-    txt_file.unlink()
-
-
-def test_from_txt_file_with_unordered_node_ids(tmp_path):
-    txt_file = tmp_path / "tmp_grid"
-    txt_file.write_text("S1 2\nS1 10\n10 11\n2 5\n5 6\n3 4\n3 7", encoding="utf-8")
-    grid = Grid.from_txt_file(txt_file)
-    txt_file.unlink()
-
-    assert 9 == grid.node.size
-
-
 def test_grid_as_str(basic_grid):
     grid = basic_grid
 
@@ -319,3 +273,73 @@ def test_grid_as_str(basic_grid):
 
     assert "102 106 301,transformer" in grid_as_string
     assert "103 104 203,open" in grid_as_string
+
+
+class TestFromTxt:
+    def test_from_txt(self):
+        txt_lines = [
+            "S1 2",
+            "S1 3 open",
+            "2 7",
+            "3 5",
+            "3 6 transformer",
+            "5 7",
+            "7 8",
+            "8 9",
+        ]
+        grid = Grid.from_txt(txt_lines)
+        assert 8 == grid.node.size
+        assert 1 == grid.branches.filter(to_status=0).size
+        assert 1 == grid.transformer.size
+        np.testing.assert_array_equal([14, 10, 11, 12, 13, 15, 16, 17], grid.branches.id)
+
+    def test_from_txt_with_branch_ids(self):
+        txt_lines = [
+            "S1 2 91",
+            "S1 3 92,open",
+            "2 7 93",
+            "3 5 94",
+            "3 6 transformer,95",
+            "5 7 96",
+            "7 8 97",
+            "8 9 98",
+        ]
+
+        grid = Grid.from_txt(txt_lines)
+        assert 8 == grid.node.size
+        assert 1 == grid.branches.filter(to_status=0).size
+        assert 1 == grid.transformer.size
+        np.testing.assert_array_equal([95, 91, 92, 93, 94, 96, 97, 98], grid.branches.id)
+
+    def test_from_txt_with_conflicting_ids(self):
+        txt_lines = [
+            "S1 2",
+            "1 3",
+        ]
+
+        with pytest.raises(ValueError):
+            Grid.from_txt(txt_lines)
+
+    def test_from_txt_with_unordered_node_ids(self):
+        txt_lines = [
+            "S1 2",
+            "S1 10",
+            "10 11",
+            "2 5",
+            "5 6",
+            "3 4",
+            "3 7",
+        ]
+        grid = Grid.from_txt(txt_lines)
+        assert 9 == grid.node.size
+
+    def test_from_txt_file(self, tmp_path):
+        txt_file = tmp_path / "tmp_grid"
+        txt_file.write_text("S1 2\nS1 3 open\n2 7\n3 5\n3 6 transformer\n5 7\n7 8\n8 9", encoding="utf-8")
+        grid = Grid.from_txt_file(txt_file)
+        txt_file.unlink()
+
+        assert 8 == grid.node.size
+        assert 1 == grid.branches.filter(to_status=0).size
+        assert 1 == grid.transformer.size
+        np.testing.assert_array_equal([14, 10, 11, 12, 13, 15, 16, 17], grid.branches.id)

From 8441e89a4db4acb74cae289b097a0c851f08d2aa Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 13:06:10 +0100
Subject: [PATCH 03/13] support unordered branches

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../_core/model/grids/_text_sources.py           |  2 +-
 tests/unit/model/grids/test_grid_base.py         | 16 +++++++++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/power_grid_model_ds/_core/model/grids/_text_sources.py b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
index dc670cb..ad85602 100644
--- a/src/power_grid_model_ds/_core/model/grids/_text_sources.py
+++ b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
@@ -110,4 +110,4 @@ def add_branch(self, branch: tuple[str, str], comments: list[str]):
             new_branch.to_status = 0
         else:
             new_branch.to_status = 1
-        self.grid.append(new_branch)
+        self.grid.append(new_branch, check_max_id=False)
diff --git a/tests/unit/model/grids/test_grid_base.py b/tests/unit/model/grids/test_grid_base.py
index 39b68a3..f341430 100644
--- a/tests/unit/model/grids/test_grid_base.py
+++ b/tests/unit/model/grids/test_grid_base.py
@@ -276,7 +276,7 @@ def test_grid_as_str(basic_grid):
 
 
 class TestFromTxt:
-    def test_from_txt(self):
+    def test_from_txt_lines(self):
         txt_lines = [
             "S1 2",
             "S1 3 open",
@@ -333,6 +333,20 @@ def test_from_txt_with_unordered_node_ids(self):
         grid = Grid.from_txt(txt_lines)
         assert 9 == grid.node.size
 
+    def test_from_txt_with_unordered_branch_ids(self):
+        txt_lines = [
+            "3 6 14, transformer",
+            "S1 2 10",
+            "S1 3 11, open",
+            "2 7 12",
+            "3 5 13",
+            "5 7 15",
+            "7 8 16",
+            "8 9 17",
+        ]
+        grid = Grid.from_txt(txt_lines)
+        assert 9 == grid.node.size
+
     def test_from_txt_file(self, tmp_path):
         txt_file = tmp_path / "tmp_grid"
         txt_file.write_text("S1 2\nS1 3 open\n2 7\n3 5\n3 6 transformer\n5 7\n7 8\n8 9", encoding="utf-8")

From a1c17b59f20a834872c74731715e70dd05e262d0 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 13:06:18 +0100
Subject: [PATCH 04/13] update documentation

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../utils/grid_from_txt_examples.ipynb        | 52 +++++++++++++++----
 1 file changed, 41 insertions(+), 11 deletions(-)

diff --git a/docs/examples/utils/grid_from_txt_examples.ipynb b/docs/examples/utils/grid_from_txt_examples.ipynb
index 1fb390d..b1588e4 100644
--- a/docs/examples/utils/grid_from_txt_examples.ipynb
+++ b/docs/examples/utils/grid_from_txt_examples.ipynb
@@ -28,13 +28,22 @@
     "- A _transformer_ is defined as `<from_node> <to_node> transformer`\n",
     "  - e.g.: `8 9 transformer`\n",
     "- A _grid opening_ is defined by adding `open`\n",
-    "  - e.g.: `4 5 open` for _lines_ or `6 7 transformer,open` for _transformers_\n",
-    "\n",
+    "  - e.g.: `4 5 open` for _lines_ or `6 7 transformer,open` for _transformers_\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
     "### Loading a drawn grid into pgm-ds\n",
     "\n",
-    "Once you've created a grid, copy the _Graph Data_ of your grid to a text file (e.g. `my_grid.txt`).\n",
+    "There are two ways of loading a text grid into a pgm-ds:\n",
+    "- load grid from a .txt file\n",
+    "- load grid from a list of strings\n",
     "\n",
-    "For example, your file could contain the following data:\n",
+    "#### Load a grid from a .txt file\n",
+    "Copy the _Graph Data_ of your grid to a text file (e.g. `my_grid.txt`).\n",
+    "For the example above, the file should contain the following data:\n",
     "\n",
     "```text\n",
     "S1 2\n",
@@ -52,12 +61,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [],
    "source": [
     "from pathlib import Path\n",
-    "\n",
     "from power_grid_model_ds import Grid\n",
     "\n",
     "txt_file_path = Path(\"../../_static/my_grid.txt\")\n",
@@ -68,12 +76,34 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "**You should now have a grid loaded from your drawn graph data!**\n"
+    "\n",
+    "#### Load grid from a list of strings\n",
+    "You can also load a grid directly from a list of strings"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from power_grid_model_ds import Grid\n",
+    "\n",
+    "grid = Grid.from_txt([\n",
+    "    \"S1 2\",\n",
+    "    \"S1 3 open\",\n",
+    "    \"2 7\",\n",
+    "    \"3 5\",\n",
+    "    \"3 6 transformer\",\n",
+    "    \"5 7\",\n",
+    "    \"7 8\",\n",
+    "    \"8 9\",\n",
+    "])"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [
     {
@@ -99,7 +129,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": ".venv",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -113,9 +143,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.3"
+   "version": "3.13.1"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }

From 0dddcf2ac9cd5c11b8934d403dc8843c8e883448 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 13:09:29 +0100
Subject: [PATCH 05/13] update gitignore

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .gitignore | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/.gitignore b/.gitignore
index 78552f6..0120a87 100644
--- a/.gitignore
+++ b/.gitignore
@@ -55,3 +55,6 @@ PYPI_VERSION
 build/
 wheelhouse/
 _build/
+
+# Jupyter Notebook
+.ipynb_checkpoints
\ No newline at end of file

From 960a09d6e8970306e9950583851cd30c13fe0547 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 13:09:33 +0100
Subject: [PATCH 06/13] update documentation

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../utils/grid_from_txt_examples.ipynb        | 23 +++++++++++--------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/docs/examples/utils/grid_from_txt_examples.ipynb b/docs/examples/utils/grid_from_txt_examples.ipynb
index b1588e4..f2a2890 100644
--- a/docs/examples/utils/grid_from_txt_examples.ipynb
+++ b/docs/examples/utils/grid_from_txt_examples.ipynb
@@ -66,6 +66,7 @@
    "outputs": [],
    "source": [
     "from pathlib import Path\n",
+    "\n",
     "from power_grid_model_ds import Grid\n",
     "\n",
     "txt_file_path = Path(\"../../_static/my_grid.txt\")\n",
@@ -89,16 +90,18 @@
    "source": [
     "from power_grid_model_ds import Grid\n",
     "\n",
-    "grid = Grid.from_txt([\n",
-    "    \"S1 2\",\n",
-    "    \"S1 3 open\",\n",
-    "    \"2 7\",\n",
-    "    \"3 5\",\n",
-    "    \"3 6 transformer\",\n",
-    "    \"5 7\",\n",
-    "    \"7 8\",\n",
-    "    \"8 9\",\n",
-    "])"
+    "grid = Grid.from_txt(\n",
+    "    [\n",
+    "        \"S1 2\",\n",
+    "        \"S1 3 open\",\n",
+    "        \"2 7\",\n",
+    "        \"3 5\",\n",
+    "        \"3 6 transformer\",\n",
+    "        \"5 7\",\n",
+    "        \"7 8\",\n",
+    "        \"8 9\",\n",
+    "    ]\n",
+    ")"
    ]
   },
   {

From ce2e0ddb61413cef79f9df71082c1196920000a0 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 13:09:37 +0100
Subject: [PATCH 07/13] fix test

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 tests/unit/model/grids/test_grid_base.py | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/tests/unit/model/grids/test_grid_base.py b/tests/unit/model/grids/test_grid_base.py
index f341430..7fea164 100644
--- a/tests/unit/model/grids/test_grid_base.py
+++ b/tests/unit/model/grids/test_grid_base.py
@@ -335,14 +335,13 @@ def test_from_txt_with_unordered_node_ids(self):
 
     def test_from_txt_with_unordered_branch_ids(self):
         txt_lines = [
-            "3 6 14, transformer",
-            "S1 2 10",
-            "S1 3 11, open",
-            "2 7 12",
-            "3 5 13",
-            "5 7 15",
-            "7 8 16",
-            "8 9 17",
+            "5 6 16",
+            "3 4 17",
+            "3 7 18",
+            "S1 2 12",
+            "S1 10 13",
+            "10 11 14",
+            "2 5 15",
         ]
         grid = Grid.from_txt(txt_lines)
         assert 9 == grid.node.size

From a7bdd9d41984a7bbe247e523a83ec14772afd035 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 14:24:35 +0100
Subject: [PATCH 08/13] switch to regex for better text support

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../_core/model/grids/_text_sources.py        | 20 +++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/power_grid_model_ds/_core/model/grids/_text_sources.py b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
index ad85602..0612957 100644
--- a/src/power_grid_model_ds/_core/model/grids/_text_sources.py
+++ b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
@@ -5,6 +5,7 @@
 """Create a grid from text a text file"""
 
 import logging
+import re
 from typing import TYPE_CHECKING
 
 from power_grid_model_ds._core.model.enums.nodes import NodeType
@@ -34,8 +35,11 @@ class TextSource:
     def __init__(self, grid_class: type["Grid"]):
         self.grid = grid_class.empty()
 
-    def load_from_txt(self, txt_lines: list[str]) -> "Grid":
+    def load_from_txt(self, txt_lines: list[str] | str) -> "Grid":
         """Load a grid from text"""
+        if isinstance(txt_lines, str):
+            txt_lines = txt_lines.split("\n")
+
         txt_nodes, txt_branches = self.read_txt(txt_lines)
         self.add_nodes(txt_nodes)
         self.add_branches(txt_branches)
@@ -50,16 +54,20 @@ def read_txt(txt_lines: list[str]) -> tuple[set, dict]:
         for text_line in txt_lines:
             if not text_line.strip() or text_line.startswith("#"):
                 continue  # skip empty lines and comments
-            try:
-                from_node_str, to_node_str, *comments = text_line.strip().split(" ")
-            except ValueError as err:
-                raise ValueError(f"Text line '{text_line}' is invalid. Skipping...") from err
-            comments = comments[0].split(",") if comments else []
+
+            pattern = re.compile(r'^\s*(\S+)\s+(\S+)(?:\s+(\S+))?\s*$')
+            match = pattern.match(text_line)
+            if not match:
+                raise ValueError(f"Text line '{text_line}' is invalid. Skipping...")
+
+            from_node_str, to_node_str, comment = match.groups()
+            comments = comment.split(",") if comment else []
 
             txt_nodes |= {from_node_str, to_node_str}
             txt_branches[(from_node_str, to_node_str)] = comments
         return txt_nodes, txt_branches
 
+
     def add_nodes(self, nodes: set[str]):
         """Add nodes to the grid"""
         source_nodes = {int(node[1:]) for node in nodes if node.startswith("S")}

From 4866e6be2cb757dc1e6a2f356ffeef87790be4a5 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 14:24:54 +0100
Subject: [PATCH 09/13] add support for both list[str] and str

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../_core/model/grids/_text_sources.py        |  3 +-
 .../_core/model/grids/base.py                 |  8 ++++--
 tests/unit/model/grids/test_grid_base.py      | 28 +++++++++----------
 3 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/src/power_grid_model_ds/_core/model/grids/_text_sources.py b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
index 0612957..c042201 100644
--- a/src/power_grid_model_ds/_core/model/grids/_text_sources.py
+++ b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
@@ -55,7 +55,7 @@ def read_txt(txt_lines: list[str]) -> tuple[set, dict]:
             if not text_line.strip() or text_line.startswith("#"):
                 continue  # skip empty lines and comments
 
-            pattern = re.compile(r'^\s*(\S+)\s+(\S+)(?:\s+(\S+))?\s*$')
+            pattern = re.compile(r"^\s*(\S+)\s+(\S+)(?:\s+(\S+))?\s*$")
             match = pattern.match(text_line)
             if not match:
                 raise ValueError(f"Text line '{text_line}' is invalid. Skipping...")
@@ -67,7 +67,6 @@ def read_txt(txt_lines: list[str]) -> tuple[set, dict]:
             txt_branches[(from_node_str, to_node_str)] = comments
         return txt_nodes, txt_branches
 
-
     def add_nodes(self, nodes: set[str]):
         """Add nodes to the grid"""
         source_nodes = {int(node[1:]) for node in nodes if node.startswith("S")}
diff --git a/src/power_grid_model_ds/_core/model/grids/base.py b/src/power_grid_model_ds/_core/model/grids/base.py
index 0721f69..717d250 100644
--- a/src/power_grid_model_ds/_core/model/grids/base.py
+++ b/src/power_grid_model_ds/_core/model/grids/base.py
@@ -409,13 +409,17 @@ def _from_pickle(cls, pickle_path: Path):
         return grid
 
     @classmethod
-    def from_txt(cls, txt_lines: list[str]):
+    def from_txt(cls, txt_lines: list[str] | str):
         """Build a grid from a list of strings
 
         See the documentation for the expected format of the txt_lines
 
-        Example:
+        Args:
+            txt_lines (list[str] | str): The lines of the txt
+
+        Examples:
             >>> Grid.from_txt(["1 2", "2 3", "3 4 transformer", "4 5", "S1 6"])
+            alternative: Grid.from_txt("1 2\n2 3\n3 4 transformer\n4 5\nS1 6")
         """
         return TextSource(grid_class=cls).load_from_txt(txt_lines)
 
diff --git a/tests/unit/model/grids/test_grid_base.py b/tests/unit/model/grids/test_grid_base.py
index 7fea164..f1e7c39 100644
--- a/tests/unit/model/grids/test_grid_base.py
+++ b/tests/unit/model/grids/test_grid_base.py
@@ -293,6 +293,14 @@ def test_from_txt_lines(self):
         assert 1 == grid.transformer.size
         np.testing.assert_array_equal([14, 10, 11, 12, 13, 15, 16, 17], grid.branches.id)
 
+    def test_from_txt_string(self):
+        txt_string = "S1 2\nS1 3 open\n2 7\n3 5\n3 6 transformer\n5 7\n7 8\n8 9"
+        assert Grid.from_txt(txt_string)
+
+    def test_from_txt_string_with_spaces(self):
+        txt_string = "S1 2     \nS1 3   open\n2    7\n3 5\n   3 6 transformer\n5 7\n7   8\n8 9"
+        assert Grid.from_txt(txt_string)
+
     def test_from_txt_with_branch_ids(self):
         txt_lines = [
             "S1 2 91",
@@ -312,25 +320,15 @@ def test_from_txt_with_branch_ids(self):
         np.testing.assert_array_equal([95, 91, 92, 93, 94, 96, 97, 98], grid.branches.id)
 
     def test_from_txt_with_conflicting_ids(self):
-        txt_lines = [
-            "S1 2",
-            "1 3",
-        ]
+        with pytest.raises(ValueError):
+            Grid.from_txt(["S1 2", "1 3"])
 
+    def test_from_txt_with_invalid_line(self):
         with pytest.raises(ValueError):
-            Grid.from_txt(txt_lines)
+            Grid.from_txt(["S1 2 arg3 arg4"])
 
     def test_from_txt_with_unordered_node_ids(self):
-        txt_lines = [
-            "S1 2",
-            "S1 10",
-            "10 11",
-            "2 5",
-            "5 6",
-            "3 4",
-            "3 7",
-        ]
-        grid = Grid.from_txt(txt_lines)
+        grid = Grid.from_txt(["S1 2", "S1 10", "10 11", "2 5", "5 6", "3 4", "3 7"])
         assert 9 == grid.node.size
 
     def test_from_txt_with_unordered_branch_ids(self):

From 2860f04ffa1b01e596f2e47f3f6d2d65f6e098f3 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 14:27:19 +0100
Subject: [PATCH 10/13] add test for docstring

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 tests/unit/model/grids/test_grid_base.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tests/unit/model/grids/test_grid_base.py b/tests/unit/model/grids/test_grid_base.py
index f1e7c39..a40b500 100644
--- a/tests/unit/model/grids/test_grid_base.py
+++ b/tests/unit/model/grids/test_grid_base.py
@@ -301,6 +301,19 @@ def test_from_txt_string_with_spaces(self):
         txt_string = "S1 2     \nS1 3   open\n2    7\n3 5\n   3 6 transformer\n5 7\n7   8\n8 9"
         assert Grid.from_txt(txt_string)
 
+    def test_from_docstring(self):
+        txt_string = """
+        S1 2
+        S1 3 open
+        2 7
+        3 5
+        3 6 transformer
+        5 7
+        7 8
+        8 9
+        """
+        assert Grid.from_txt(txt_string)
+
     def test_from_txt_with_branch_ids(self):
         txt_lines = [
             "S1 2 91",

From 8124ef20e330fcff9f125364c04108c457a49b43 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 14:51:31 +0100
Subject: [PATCH 11/13] switch to args input

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../_core/model/grids/_text_sources.py        |  8 ++--
 .../_core/model/grids/base.py                 | 10 ++---
 tests/unit/model/grids/test_grid_base.py      | 42 +++++--------------
 3 files changed, 20 insertions(+), 40 deletions(-)

diff --git a/src/power_grid_model_ds/_core/model/grids/_text_sources.py b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
index c042201..89b7048 100644
--- a/src/power_grid_model_ds/_core/model/grids/_text_sources.py
+++ b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
@@ -35,12 +35,12 @@ class TextSource:
     def __init__(self, grid_class: type["Grid"]):
         self.grid = grid_class.empty()
 
-    def load_from_txt(self, txt_lines: list[str] | str) -> "Grid":
+    def load_from_txt(self, *args: str) -> "Grid":
         """Load a grid from text"""
-        if isinstance(txt_lines, str):
-            txt_lines = txt_lines.split("\n")
 
-        txt_nodes, txt_branches = self.read_txt(txt_lines)
+        text_lines = [line for arg in args for line in arg.strip().split("\n")]
+
+        txt_nodes, txt_branches = self.read_txt(text_lines)
         self.add_nodes(txt_nodes)
         self.add_branches(txt_branches)
         self.grid.set_feeder_ids()
diff --git a/src/power_grid_model_ds/_core/model/grids/base.py b/src/power_grid_model_ds/_core/model/grids/base.py
index 717d250..7af482c 100644
--- a/src/power_grid_model_ds/_core/model/grids/base.py
+++ b/src/power_grid_model_ds/_core/model/grids/base.py
@@ -409,19 +409,19 @@ def _from_pickle(cls, pickle_path: Path):
         return grid
 
     @classmethod
-    def from_txt(cls, txt_lines: list[str] | str):
+    def from_txt(cls, *args: str):
         """Build a grid from a list of strings
 
         See the documentation for the expected format of the txt_lines
 
         Args:
-            txt_lines (list[str] | str): The lines of the txt
+            *args (str): The lines of the grid
 
         Examples:
-            >>> Grid.from_txt(["1 2", "2 3", "3 4 transformer", "4 5", "S1 6"])
+            >>> Grid.from_txt("1 2", "2 3", "3 4 transformer", "4 5", "S1 6")
             alternative: Grid.from_txt("1 2\n2 3\n3 4 transformer\n4 5\nS1 6")
         """
-        return TextSource(grid_class=cls).load_from_txt(txt_lines)
+        return TextSource(grid_class=cls).load_from_txt(*args)
 
     @classmethod
     # pylint: disable=arguments-differ
@@ -433,7 +433,7 @@ def from_txt_file(cls, txt_file_path: Path):
         """
         with open(txt_file_path, "r", encoding="utf-8") as f:
             txt_lines = f.readlines()
-        return TextSource(grid_class=cls).load_from_txt(txt_lines)
+        return TextSource(grid_class=cls).load_from_txt(*txt_lines)
 
     def set_feeder_ids(self):
         """Sets feeder and substation id properties in the grids arrays"""
diff --git a/tests/unit/model/grids/test_grid_base.py b/tests/unit/model/grids/test_grid_base.py
index a40b500..db10df7 100644
--- a/tests/unit/model/grids/test_grid_base.py
+++ b/tests/unit/model/grids/test_grid_base.py
@@ -277,7 +277,7 @@ def test_grid_as_str(basic_grid):
 
 class TestFromTxt:
     def test_from_txt_lines(self):
-        txt_lines = [
+        grid = Grid.from_txt(
             "S1 2",
             "S1 3 open",
             "2 7",
@@ -286,8 +286,7 @@ def test_from_txt_lines(self):
             "5 7",
             "7 8",
             "8 9",
-        ]
-        grid = Grid.from_txt(txt_lines)
+        )
         assert 8 == grid.node.size
         assert 1 == grid.branches.filter(to_status=0).size
         assert 1 == grid.transformer.size
@@ -302,7 +301,7 @@ def test_from_txt_string_with_spaces(self):
         assert Grid.from_txt(txt_string)
 
     def test_from_docstring(self):
-        txt_string = """
+        assert Grid.from_txt("""
         S1 2
         S1 3 open
         2 7
@@ -311,22 +310,12 @@ def test_from_docstring(self):
         5 7
         7 8
         8 9
-        """
-        assert Grid.from_txt(txt_string)
+        """)
 
     def test_from_txt_with_branch_ids(self):
-        txt_lines = [
-            "S1 2 91",
-            "S1 3 92,open",
-            "2 7 93",
-            "3 5 94",
-            "3 6 transformer,95",
-            "5 7 96",
-            "7 8 97",
-            "8 9 98",
-        ]
-
-        grid = Grid.from_txt(txt_lines)
+        grid = Grid.from_txt(
+            "S1 2 91", "S1 3 92,open", "2 7 93", "3 5 94", "3 6 transformer,95", "5 7 96", "7 8 97", "8 9 98"
+        )
         assert 8 == grid.node.size
         assert 1 == grid.branches.filter(to_status=0).size
         assert 1 == grid.transformer.size
@@ -334,27 +323,18 @@ def test_from_txt_with_branch_ids(self):
 
     def test_from_txt_with_conflicting_ids(self):
         with pytest.raises(ValueError):
-            Grid.from_txt(["S1 2", "1 3"])
+            Grid.from_txt("S1 2", "1 3")
 
     def test_from_txt_with_invalid_line(self):
         with pytest.raises(ValueError):
-            Grid.from_txt(["S1 2 arg3 arg4"])
+            Grid.from_txt("S1 2 arg3 arg4")
 
     def test_from_txt_with_unordered_node_ids(self):
-        grid = Grid.from_txt(["S1 2", "S1 10", "10 11", "2 5", "5 6", "3 4", "3 7"])
+        grid = Grid.from_txt("S1 2", "S1 10", "10 11", "2 5", "5 6", "3 4", "3 7")
         assert 9 == grid.node.size
 
     def test_from_txt_with_unordered_branch_ids(self):
-        txt_lines = [
-            "5 6 16",
-            "3 4 17",
-            "3 7 18",
-            "S1 2 12",
-            "S1 10 13",
-            "10 11 14",
-            "2 5 15",
-        ]
-        grid = Grid.from_txt(txt_lines)
+        grid = Grid.from_txt("5 6 16", "3 4 17", "3 7 18", "S1 2 12", "S1 10 13", "10 11 14", "2 5 15")
         assert 9 == grid.node.size
 
     def test_from_txt_file(self, tmp_path):

From 84863dcb74ab63cd0be02a9d133caf4ab182b255 Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 15:19:29 +0100
Subject: [PATCH 12/13] remove re module implementation

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 .../_core/model/grids/_text_sources.py            | 15 ++++++---------
 tests/unit/model/grids/test_grid_base.py          |  2 +-
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/src/power_grid_model_ds/_core/model/grids/_text_sources.py b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
index 89b7048..ab9c1a9 100644
--- a/src/power_grid_model_ds/_core/model/grids/_text_sources.py
+++ b/src/power_grid_model_ds/_core/model/grids/_text_sources.py
@@ -5,7 +5,6 @@
 """Create a grid from text a text file"""
 
 import logging
-import re
 from typing import TYPE_CHECKING
 
 from power_grid_model_ds._core.model.enums.nodes import NodeType
@@ -49,19 +48,17 @@ def load_from_txt(self, *args: str) -> "Grid":
     @staticmethod
     def read_txt(txt_lines: list[str]) -> tuple[set, dict]:
         """Extract assets from text"""
+
         txt_nodes = set()
         txt_branches = {}
         for text_line in txt_lines:
             if not text_line.strip() or text_line.startswith("#"):
                 continue  # skip empty lines and comments
-
-            pattern = re.compile(r"^\s*(\S+)\s+(\S+)(?:\s+(\S+))?\s*$")
-            match = pattern.match(text_line)
-            if not match:
-                raise ValueError(f"Text line '{text_line}' is invalid. Skipping...")
-
-            from_node_str, to_node_str, comment = match.groups()
-            comments = comment.split(",") if comment else []
+            try:
+                from_node_str, to_node_str, *comments = text_line.strip().split()
+            except ValueError as err:
+                raise ValueError(f"Text line '{text_line}' is invalid. Skipping...") from err
+            comments = comments[0].split(",") if comments else []
 
             txt_nodes |= {from_node_str, to_node_str}
             txt_branches[(from_node_str, to_node_str)] = comments
diff --git a/tests/unit/model/grids/test_grid_base.py b/tests/unit/model/grids/test_grid_base.py
index db10df7..fd1d1b6 100644
--- a/tests/unit/model/grids/test_grid_base.py
+++ b/tests/unit/model/grids/test_grid_base.py
@@ -327,7 +327,7 @@ def test_from_txt_with_conflicting_ids(self):
 
     def test_from_txt_with_invalid_line(self):
         with pytest.raises(ValueError):
-            Grid.from_txt("S1 2 arg3 arg4")
+            Grid.from_txt("S1")
 
     def test_from_txt_with_unordered_node_ids(self):
         grid = Grid.from_txt("S1 2", "S1 10", "10 11", "2 5", "5 6", "3 4", "3 7")

From 0018e2feb3495870654da832367a9a1161f9529d Mon Sep 17 00:00:00 2001
From: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Date: Wed, 5 Feb 2025 15:19:46 +0100
Subject: [PATCH 13/13] bump minor

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
---
 VERSION | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/VERSION b/VERSION
index 9f8e9b6..b123147 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.0
\ No newline at end of file
+1.1
\ No newline at end of file