Add experiment with file options

Author: gjbex

source-code/command-line-arguments/ArgParse/README.md

@@ -23,3 +23,4 @@ $ ./generate_gaussian.py -h
    ./options_in_file.py --foo something @file_options.txt
    ```
 1. `file_options.txt`: file containing options for `options_in_file.py`.
+1. `Rerun`: experiment with file options.

source-code/command-line-arguments/ArgParse/Rerun/README.md

@@ -0,0 +1,33 @@
+# Rerunnable
+
+Toy application to explore the possibilities created by
+using argparse options stored in a file.
+
+
+## What is it?
+1.  rerunnable.py`: script to explore the possibilities.
+
+
+## How to use?
+
+```bash
+$ ./rerunnable.py  --verbose  --number 5  --type bye  gjb
+$ ./rerunnable.py @rerunnable_cla.txt
+```
+
+This will rerun the application with all the settings specified for the
+previous run.
+
+To override options:
+```bash
+$ ./rerunnable.py  @rerunnable_cla.txt --number 3
+```
+
+
+## Conclusions
+
+This approach works well for command line options, e.g., `--number 5`.
+
+It is not flexibile for flags, e.g., `--verbose` since they can not be "unset".
+
+It is not flexible either for positional arguments since they can not be modified.

source-code/command-line-arguments/ArgParse/Rerun/rerunnable.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python
+
+import argparse
+
+
+def dump_options(options, pos_args=None, exclude=None):
+    options_dict = vars(options)
+    with open('rerunnable_cla.txt', 'w') as file:
+        for key, value in options_dict.items():
+            if ((exclude is None or key not in exclude) and
+                (pos_args is None or key not in pos_args)):
+                if isinstance(value, bool):
+                    if value:
+                        print(f'--{key}', file=file)
+                else:
+                    print(f'--{key}\n{value}', file=file)
+        if pos_args is not None:
+            for key in pos_args:
+                print(options_dict[key], file=file)
+
+
+if __name__ == '__main__':
+    arg_parser = argparse.ArgumentParser(
+        fromfile_prefix_chars='@',
+        description='application that saves its command line options and can be rerun'
+    )
+    arg_parser.add_argument('--number', type=int, default=1,
+                            help='number of messages to write')
+    arg_parser.add_argument('--type', choices=('hello', 'bye'), default='hello',
+                            help='message type')
+    arg_parser.add_argument('--verbose', action='store_true',
+                            help='verbose output')
+    arg_parser.add_argument('name', help='person to message')
+    options = arg_parser.parse_args()
+    dump_options(options, pos_args=('name', ))
+    if options.verbose:
+        print(f'printing {options.number} messages')
+    for _ in range(options.number):
+        print(f'{options.type} {options.name}')