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?
#!/usr/bin/env python
"""
Usage: script.py
This describes the script.
"""
import sys
if len(sys.argv) < 2:
print("<here comes the docstring>")
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.
help(module_name) after you import that module.
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
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)
"""Usage: {scriptName}""".format(scriptName = sys.argv[0])
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 --helppython3 yourscriptname.py --helpAn 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.
