CODEWITHSUNDEEP
pythondocstring
thias
thias

Reputation: 2440

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

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>")

Upvotes: 104

Views: 45422

Answers (5)

thehale
thehale

Reputation: 1756

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.

Upvotes: 2

Mr CaT
Mr CaT

Reputation: 337

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

Upvotes: 1

Martin Thoma
Martin Thoma

Reputation: 136327

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

Upvotes: 20

ﾠﾠﾠ
ﾠﾠﾠ

Reputation: 66950

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.

Upvotes: 124

wint3rschlaefer
wint3rschlaefer

Reputation: 309

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)

Upvotes: 15

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