不区分大小写的 arparse 选择

是否有可能以不区分大小写的方式检查 Argparse 选择？

import argparse
choices = ["win64", "win32"]
parser = argparse.ArgumentParser()
parser.add_argument("-p", choices=choices)
print(parser.parse_args(["-p", "Win32"]))

结果:

usage: choices.py [-h] [-p {win64,win32}]
choices.py: error: argument -p: invalid choice: 'Win32' (choose from 'win64','win32')
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最佳答案

Transform the argument into lowercase by using

type = str.lower

for the -p switch.

This solution was pointed out by chepner in a comment. The solution I proposed earlier was

type = lambda s : s.lower()

which is also valid, but it's simpler to just use str.lower.

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Using lower in the type is nice way of doing this, if you don't mind loosing the case information.

If you want to retain the case, you could define a custom choices class. The choices needs two methods, __contains__ (for testing in), and iteration (to list the choices).

class mylist(list):
# list subclass that uses lower() when testing for 'in'
def __contains__(self, other):
return super(mylist,self).__contains__(other.lower())
choices=mylist(['win64','win32'])
parser = argparse.ArgumentParser()
parser.add_argument("-p", choices=choices)
print(parser.parse_args(["-p", "Win32"]))
# Namespace(p='Win32')

The help is:

usage: ipython [-h] [-p {win64,win32}]


optional arguments:
-h, --help        show this help message and exit
-p {win64,win32}
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Keeping the case information would also be possible with a one liner: 

type = lambda arg: {x.lower(): x for x in choices}[arg.lower()],

Where choices would be the same list as passed to the choices parameter.

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To clarify @5gon12eder's answer, you need to include the "type" as another paramater to add_argument:

parser.add_argument("-p", choices=choices, type=str.lower)

This will make sure that the input is lowercased.
Make sure to NOT add parentheses after lower.


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