Confusion over open() built-in function #9
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after a little hack of pylinter def open(file, mode, buffering, encoding, errors, newline, closefd, opener) -> typing.Any:
"""
Open file and return a stream. Raise OSError upon failure.
file is either a text or byte string giving the name (and the path
nif the file isn't in the current working directory) of the file to
be opened or an integer file descriptor of the file to be
wrapped. (If a file descriptor is given, it is closed when the
returned I/O object is closed, unless closefd is set to False.)
mode is an optional string that specifies the mode in which the file
is opened. It defaults to 'r' which means open for reading in text
mode. Other common values are 'w' for writing (truncating the file if
it already exists), 'x' for creating and writing to a new file, and
'a' for appending (which on some Unix systems, means that all writes
append to the end of the file regardless of the current seek position).
In text mode, if encoding is not specified the encoding used is platform
dependent: locale.getpreferredencoding(False) is called to get the
current locale encoding. (For reading and writing raw bytes use binary
mode and leave encoding unspecified.) The available modes are:
========= ===============================================================
Character Meaning--------- ---------------------------------------------------------------
'r' open for reading (default)
'w' open for writing, truncating the file first
'x' create a new file and open it for writing
'a' open for writing, appending to the end of the file if it exists
'b' binary mode
't' text mode (default)
'+' open a disk file for updating (reading and writing)
'U' universal newline mode (deprecated)
========= ===============================================================
The default mode is 'rt' (open for reading text). For binary random
access, the mode 'w+b' opens and truncates the file to 0 bytes, while
'r+b' opens the file without truncation. The 'x' mode implies 'w' and
raises an `FileExistsError` if the file already exists.
Python distinguishes between files opened in binary and text modes,
even when the underlying operating system doesn't. Files opened in
binary mode (appending 'b' to the mode argument) return contents as
bytes objects without any decoding. In text mode (the default, or when
't' is appended to the mode argument), the contents of the file are
returned as strings, the bytes having been first decoded using a
platform-dependent encoding or using the specified encoding if given.
'U' mode is deprecated and will raise an exception in future versions
of Python. It has no effect in Python 3. Use newline to control
universal newlines mode.
buffering is an optional integer used to set the buffering policy.
Pass 0 to switch buffering off (only allowed in binary mode), 1 to select
line buffering (only usable in text mode), and an integer > 1 to indicate
the size of a fixed-size chunk buffer. When no buffering argument is
given, the default buffering policy works as follows:
- Binary files are buffered in fixed-size chunks; the size of the buffer
is chosen using a heuristic trying to determine the underlying device's
'block size' and falling back on `io.DEFAULT_BUFFER_SIZE`.
On many systems, the buffer will typically be 4096 or 8192 bytes long.
- \"Interactive\" text files (files for which isatty() returns True)
use line buffering. Other text files use the policy described above for binary files.
encoding is the name of the encoding used to decode or encode the file.
This should only be used in text mode. The default encoding is platform dependent, but any
encoding supported by Python can be passed. See the codecs module for the list of supported encodings.
errors is an optional string that specifies how encoding errors are to be handled---this argument should
not be used in binary mode. Pass 'strict' to raise a ValueError exception if there is an encoding error
(the default of None has the same effect), or pass 'ignore' to ignore errors. (Note that ignoring
encoding errors can lead to data loss.) See the documentation for codecs.register or run
'help(codecs.Codec)' for a list of the permitted encoding error strings.
newline controls how universal newlines works (it only applies to text mode).
It can be None, '', '\n', '\r', and '\r\n'. It works as follows:
- On input, if newline is None, universal newlines mode is enabled.
Lines in the input can end in '\n', '\r', or '\r\n', and these are translated into '\n' before being returned to the caller.
If it is '', universal newline mode is enabled, but line endings are returned to the caller untranslated.
If it has any of the other legal values, input lines are only terminated by the given string, and the line ending is returned to the caller untranslated.
- On output, if newline is None, any '\n' characters written are translated to the system default line separator, os.linesep.
If newline is '' or '\n', no translation takes place.
If newline is any of the other legal values, any '\n' characters written are translated to the given string.
If closefd is False, the underlying file descriptor will be kept open when the file is closed.
This does not work when a file name is given and must be True in that case.
A custom opener can be used by passing a callable as *opener*.
The underlying file descriptor for the file object is then obtained by calling *opener* with (*file*, *flags*).
*opener* must return an open file descriptor (passing os.open as *opener* results in functionality similar to passing None).
open() returns a file object whose type depends on the mode, and through which the standard file operations
such as reading and writing are performed. When open() is used to open a file in a text mode ('w', 'r', 'wt', 'rt', etc.),
it returns a TextIOWrapper. When used to open a file in a binary mode, the returned class varies:
in read binary mode, it returns a BufferedReader; in write binary and append binary modes,
it returns a BufferedWriter, and in read/write mode, it returns a BufferedRandom.
It is also possible to use a string or bytearray as a file for both reading and writing.
For strings StringIO can be used like a file opened in a text mode,
and for bytes a BytesIO can be used like a file opened in a binary mode.
""" |
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from _typeshed import AnyPath, OpenBinaryMode, OpenBinaryModeReading, OpenBinaryModeUpdating, OpenBinaryModeWriting, OpenTextMode
from asyncio import AbstractEventLoop
from typing import Any, Callable, Optional, Union, overload
from typing_extensions import Literal
from ..base import AiofilesContextManager
from .binary import AsyncBufferedIOBase, AsyncBufferedReader, AsyncFileIO, _UnknownAsyncBinaryIO
from .text import AsyncTextIOWrapper
_OpenFile = Union[AnyPath, int]
_Opener = Callable[[str, int], int]
# Text mode: always returns AsyncTextIOWrapper
@overload
def open(
file: _OpenFile,
mode: OpenTextMode = ...,
buffering: int = ...,
encoding: Optional[str] = ...,
errors: Optional[str] = ...,
newline: Optional[str] = ...,
closefd: bool = ...,
opener: Optional[_Opener] = ...,
*,
loop: Optional[AbstractEventLoop] = ...,
executor: Optional[Any] = ...,
) -> AiofilesContextManager[None, None, AsyncTextIOWrapper]: ...
# Unbuffered binary: returns a FileIO
@overload
def open(
file: _OpenFile,
mode: OpenBinaryMode,
buffering: Literal[0],
encoding: None = ...,
errors: None = ...,
newline: None = ...,
closefd: bool = ...,
opener: Optional[_Opener] = ...,
*,
loop: Optional[AbstractEventLoop] = ...,
executor: Optional[Any] = ...,
) -> AiofilesContextManager[None, None, AsyncFileIO]: ...
# Buffered binary reading/updating: AsyncBufferedReader
@overload
def open(
file: _OpenFile,
mode: Union[OpenBinaryModeReading, OpenBinaryModeUpdating],
buffering: Literal[-1, 1] = ...,
encoding: None = ...,
errors: None = ...,
newline: None = ...,
closefd: bool = ...,
opener: Optional[_Opener] = ...,
*,
loop: Optional[AbstractEventLoop] = ...,
executor: Optional[Any] = ...,
) -> AiofilesContextManager[None, None, AsyncBufferedReader]: ...
# Buffered binary writing: AsyncBufferedIOBase
@overload
def open(
file: _OpenFile,
mode: OpenBinaryModeWriting,
buffering: Literal[-1, 1] = ...,
encoding: None = ...,
errors: None = ...,
newline: None = ...,
closefd: bool = ...,
opener: Optional[_Opener] = ...,
*,
loop: Optional[AbstractEventLoop] = ...,
executor: Optional[Any] = ...,
) -> AiofilesContextManager[None, None, AsyncBufferedIOBase]: ...
# Buffering cannot be determined: fall back to _UnknownAsyncBinaryIO
@overload
def open(
file: _OpenFile,
mode: OpenBinaryMode,
buffering: int,
encoding: None = ...,
errors: None = ...,
newline: None = ...,
closefd: bool = ...,
opener: Optional[_Opener] = ...,
*,
loop: Optional[AbstractEventLoop] = ...,
executor: Optional[Any] = ...,
) -> AiofilesContextManager[None, None, _UnknownAsyncBinaryIO]: ... |
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@cpwood I am now going to try and get my head around this wonderful python typing conundrum - open ps. Thursday was close you will need to better this coming Saturday ;) |
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from Ptyhon 3.4 open open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)would transpose to: @overload
def open(
file: _OpenFile,
mode: Optional[OpenTextMode] | Optional[OpenBinaryMode] = 'r',
buffering: Optional[int |Literal[0]] = -1,
encoding: Optional[str] = ...,
errors: Optional[str] = ...,
newline: Optional[str] = ...,
closefd: bool = True,
opener: Optional[_Opener] = ...,
) -> AiofilesContextManager[None, None, AsyncTextIOWrapper | AsyncFileIO]: ...
"""
Open file and return a corresponding file object. If the file cannot be opened, an OSError is raised.
- The default mode is 'r' (open for reading text, synonym of 'rt').
- For binary read-write access, the mode 'w+b' opens and truncates the file to 0 bytes. 'r+b' opens the file without truncation.
- documentation: 'https://docs.python.org/3.4/library/functions.html?highlight=open#open'
"""ellipses in stubs due to pep-484 |
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@cpwood Second stab in pond, need to be brought in Pico stubs
from ..base import AiofilesContextManager
from .binary import AsyncFileIO
from .text import AsyncTextIOWrapper# Text mode: always returns a AsyncTextIOWrapper
@overload
def open(
file: _OpenFile,
mode: OpenTextMode = ...,
buffering: int = ...,
encoding: Optional[str] = ...,
errors: Optional[str] = ...,
newline: Optional[str] = ...,
closefd: bool = ...,
opener: Optional[_Opener] = ...,
) -> AiofilesContextManager[None, None, AsyncTextIOWrapper]: ...# Unbuffered binary mode: returns a AsyncFileIO
@overload
def open(
file: _OpenFile,
mode: OpenBinaryMode,
buffering: Literal[0],
encoding: None = ...,
errors: None = ...,
newline: None = ...,
closefd: bool = ...,
opener: Optional[_Opener] = ...,
) -> AiofilesContextManager[None, None, AsyncFileIO]: ...can we turn off .vscode/extensions/ms-python.vscode-pylance-2021.4.3/dist/bundled/native-stubs/lxml/etree.pyi:4447: """
Open file and return a corresponding file object. If the file cannot be opened, an OSError is raised.
- The default mode is 'r' (open for reading text, synonym of 'rt').
- For binary read-write access, the mode 'w+b' opens and truncates the file to 0 bytes. 'r+b' opens the file without truncation.
- documentation: 'https://docs.python.org/3.4/library/functions.html?highlight=open#open'
""" |
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Looks like
open()can return either aTextIOWrapperor aFileIOclass depending upon the string value of themodeparameter:from builtins.pyi
However, this causes this issue with Pylance:
The methods on both
TextIOWrapperandFileIOare identical (see uio.pyi). We should probably merge the two calls together somehow to resolve the above issue and return aGenericIOclass purely for linting and auto-complete purposes.The text was updated successfully, but these errors were encountered: