How can I print a Python file's docstring when executing it?

Question

I have a Python script with a docstring. When the parsing of the command-line arguments does not succeed, I want to print the docstring for the user’s information.

Is there any way to do this?

Minimal example

#!/usr/bin/env python
"""
Usage: script.py

This describes the script.
"""

import sys


if len(sys.argv) < 2:
    print("<here comes the docstring>")

Asked By: thias

||

Source

Answer 1

The docstring is stored in the module’s __doc__ global.

print(__doc__)

By the way, this goes for any module: import sys; print(sys.__doc__). Docstrings of functions and classes are also in their __doc__ attribute.

Answered By: Petr Viktorin

Answer 2

Here is an alternative that does not hardcode the script’s filename, but instead uses sys.argv[0] to print it. Using %(scriptName)s instead of %s improves readability of the code.

#!/usr/bin/env python
"""
Usage: %(scriptName)s

This describes the script.
"""

import sys
if len(sys.argv) < 2:
   print __doc__ % {'scriptName' : sys.argv[0].split("/")[-1]}
   sys.exit(0)

Answered By: wint3rschlaefer

Answer 3

Argument parsing should always be done with argparse.

You can display the __doc__ string by passing it to the description parameter of Argparse:

#!/usr/bin/env python
"""
This describes the script.
"""


if __name__ == '__main__':
    from argparse import ArgumentParser
    parser = ArgumentParser(description=__doc__)
    # Add your arguments here
    parser.add_argument("-f", "--file", dest="myFilenameVariable",
                        required=True,
                        help="write report to FILE", metavar="FILE")
    args = parser.parse_args()
    print(args.myFilenameVariable)

If you call this mysuperscript.py and execute it you get:

$ ./mysuperscript.py --help
usage: mysuperscript.py [-h] -f FILE

This describes the script.

optional arguments:
  -h, --help            show this help message and exit
  -f FILE, --file FILE  write report to FILE

Answered By: Martin Thoma

Answer 4

This will print the __doc__ string when --help is the only argument.

if __name__=='__main__':
 if len(sys.argv)==2 and sys.argv[1]=='--help':
    print(__doc__)

Works for both:

./yourscriptname.py --help
python3 yourscriptname.py --help

Answered By: Mr CaT

Answer 5

An enhancement of @MartinThoma’s answer so it prints multi-line docstrings inspired by Python argparse: How to insert newline in the help text?.

Argument parsing should always be done with argparse.

You can display the doc string by passing it to the description
parameter of Argparse:

#!/usr/bin/env python 
""" 
This summarizes the script.

Additional descriptive paragraph(s).
"""  # Edited this docstring


if __name__ == '__main__':
    from argparse import ArgumentParser, RawTextHelpFormatter  # Edited this line
    parser = ArgumentParser(description=__doc__
                            formatter_class=RawTextHelpFormatter)  # Added this line
    # Add your arguments here
    parser.add_argument("-f", "--file", dest="myFilenameVariable",
                        required=True,
                        help="write report to FILE", metavar="FILE")
    args = parser.parse_args()
    print(args.myFilenameVariable)

If you call this mysuperscript.py and execute it you get:

$ ./mysuperscript.py --help
usage: mysuperscript.py [-h] -f FILE

This summarizes the script.

Additional descriptive paragraph(s).

optional arguments:
  -h, --help            show this help message and exit
  -f FILE, --file FILE  write report to FILE

Without the addition of the formatter_class the output would not have the line break in the docstring.

Answered By: thehale

How can I print a Python file's docstring when executing it?

Question:

Minimal example

Answers: