Peter Otten wrote:
> Matt wrote:
>
>> What is easiest way to determine if a string ONLY contains a-z upper
>> or lowercase. I also want to allow the "-" and "_" symbols. No
>> spaces or anything else.
>
> If you don't know regular expressions here's a method where not much can
> go wrong:
... with the exception of the empty string.
If you want to reject empty strings you need to add an explicit test:
if s and acceptable(s):
print("OK")
>>>> import string
>>>> acceptable = frozenset(string.ascii_letters + "_-").issuperset
>>>> acceptable("Foo-Bar")
> True
>>>> acceptable("Foo-Bar42")
> False
>>>> acceptable("Foo Bar")
> False
>>>> acceptable(string.ascii_letters + "_-")
> True
By the way, I find that behaviour more intuitive than that of the
str.isXXX() methods as e. g.
s.isdigit()
will differ from
all(c.isdigit() for c in s)
for the empty string.
What do you think, are all apples in an empty basket red or not?
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