Add reading options from file illustration

Author: gjbex

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

@@ -14,7 +14,12 @@ $ ./generate_gaussian.py -h
 1. `partial_parse.py`: illustrate how to parse only known arguments.
 1. `two_stage_parse.py`: parsing input from a file as if it were command
    line arguments (using `shlex`) and merging with command line arguments.
-```bash
-$ ./two_stage_parse.py  -l mem=8gb -I job_script.pbs -k oe
-```
-`. `job_script.pbs`: file to use with `two_stage_parse.py`.
+   ```bash
+   $ ./two_stage_parse.py  -l mem=8gb -I job_script.pbs -k oe
+   ```
+1. `job_script.pbs`: file to use with `two_stage_parse.py`.
+1. `options_in_file.py`: illustration of how to read options from a file.
+   ```bash
+   ./options_in_file.py --foo something @file_options.txt
+   ```
+1. `file_options.txt`: file containing options for `options_in_file.py`.

source-code/command-line-arguments/ArgParse/file_options.txt

@@ -0,0 +1,3 @@
+--foo
+This is the foo value
+--flag

source-code/command-line-arguments/ArgParse/options_in_file.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python
+
+import argparse
+
+
+def amin():
+    arg_parser = argparse.ArgumentParser(fromfile_prefix_chars='@')
+    arg_parser.add_argument('--foo', help='foo option')
+    arg_parser.add_argument('--bar', help='bar optoin')
+    arg_parser.add_argument('--flag', action='store_true',
+                            help='flag option')
+    options = arg_parser.parse_args()
+    print(options)
+
+if __name__ == '__main__':
+    amin()