On Mon, Jul 12, 2021 at 12:34 PM Chris Angelico <ros...@gmail.com> wrote:
> On Tue, Jul 13, 2021 at 5:22 AM lucas <lu...@bourneuf.net> wrote:
> > Running CPython on it will raise a TypeError, and running Mypy on it
> > will indicate that no issues were found.
> >
> > I was wondering if there is any way for me to have mypy detecting the
> > args.n type, based on the type keyword of the parser.add_argument
> function ?
> >
> > It appears that some type annotations were added to tierce party
> > modules, provided by mypy itself. Is there a technical issue preventing
> > such work to be made for argparse (or other CLI ; i didn't find anything
> > for others either)
> >
>
> Seems complicated, since it depends on a lot of run-time information.
> What if you flip the problem on its head? Instead of creating the
> argparser and letting that govern the types, maybe create a dataclass,
> and then programmatically build the parser.
>
This is why I eschew argparse. I instead frequently do something like:
def usage(retval):
"""Output a usage message."""
if retval:
write = sys.stderr.write
else:
write = sys.stdout.write
write(f'{sys.argv[0]} --age 50 --help\n')
sys.exit(retval)
def main():
"""Compute maximum heart rate as a function of age."""
age = -1
while sys.argv[1:]:
if sys.argv[1] == '--age':
age = float(sys.argv[2])
del sys.argv[1]
elif sys.argv[1] in ('-h', '--help'):
usage(0)
else:
sys.stderr.write(f'{sys.argv[0]}: unrecognized option:
{sys.argv[1]}\n')
usage(1)
del sys.argv[1]
if age == -1:
sys.stderr.write('--age is a required option\n')
usage(1)
It is of course a little more typing, but tools like mypy and pylint are
much more effective this way. This is a small program, but in a large one,
this approach can really help with correctness.
If someone has a mypy extension/plugin that can do argparse as well, I may
switch. Until then....
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