How to make argparse print usage when no option is given to the code [duplicate]

Question

With the following code:

import argparse
parser = argparse.ArgumentParser(description="Prepare something code.")
parser.add_argument("-t","--tabular", help="print something in tabular way for EXCEL",
                      action="store_true")
parser.add_argument("-v","--verbose", action="store_true")
args = parser.parse_args()
if args.tabular:
    print "Tabular print"
elif args.verbose:
    print "VERBOSE"

It's only when I execute it the following way, that it prints usage:

$ python mycode.py -h
usage: mycode.py [-h] [-t] [-v]

Prepare something code.

optional arguments:
  -h, --help     show this help message and exit
  -t, --tabular  print something in tabular way for EXCEL
  -v, --verbose

What I want to do is to simply run the code: $ my code.py without any -h option whatsoever to print the usage. How can I do that?

Answer 1

That 2010 question covers the same thing, but only has 1 answer. While that answer comes indirectly from the designer of argparse, it does not cover all possibilities.

Here's one which surprised me as to its simplicity:

import sys
parser = ...
if len(sys.argv)==1:
    parser.print_help()
    # parser.print_usage() # for just the usage line
    parser.exit()
args = parser.parse_args()

Yes you can check all the namespace args for default values, but that gets old if there are many arguments. But here I am just checking whether there are any argument strings. If none, then call the parser's own help function.

ipython does something like this to generate help. It checks sys.argv for some version of help, and produces its own help message(s), before even defining the parser.

Answer 2

import argparse
parser = argparse.ArgumentParser(description="Prepare something code.")
parser.add_argument("-t","--tabular", help="print something in tabular way for EXCEL",
                      action="store_true")
parser.add_argument("-v","--verbose", action="store_true")
args = parser.parse_args()
if args.tabular:
    print "Tabular print"
elif args.verbose:
    print "VERBOSE"
else:
    print parser.print_help()