Finding all possible case permutations in Python

问题

I need to work out a list of all possible permutations of case only in python for example with input of ar it would return [ 'ar','Ar','aR','AR']
or arc [ 'arc','Arc','ARc','aRc','aRC','ARC'] and I know there is likely some Nice method but for the life of me I can not figure it out.

回答1:

def all_casings(input_string):
    if not input_string:
        yield ""
    else:
        first = input_string[:1]
        if first.lower() == first.upper():
            for sub_casing in all_casings(input_string[1:]):
                yield first + sub_casing
        else:
            for sub_casing in all_casings(input_string[1:]):
                yield first.lower() + sub_casing
                yield first.upper() + sub_casing

---

>>> [x for x in all_casings("foo")]
['foo', 'Foo', 'fOo', 'FOo', 'foO', 'FoO', 'fOO', 'FOO']
>>> list(all_casings("foo"))
['foo', 'Foo', 'fOo', 'FOo', 'foO', 'FoO', 'fOO', 'FOO']

来源：https://stackoverflow.com/questions/6792803/finding-all-possible-case-permutations-in-python