有没有办法查看字符串是否包含Python中的任何符号？

Question

I don't mean specific characters, I just mean anything that isn't alphanumeric. I've tried asking if the string contains only alphabetic and numeric characters like so:

if userInput.isalpha() and userInput.isdigit() == False:
    print ("Not valid, contains symbols or spaces")

but this doesn't work and and denies all passwords I put in.

Answer 1

Firstly, you can't be only alpha and only numeric, so your expression will always be false.

Secondly the methods isalpha() and isdigit() equate to True or False , so no need to use == False .

I would suggest using .isalnum() .

If that doesn't satisfy you're requirements you should use a regex.

alnum looks for both: https://docs.python.org/2/library/stdtypes.html#str.isalnum and works in Python 3.x and 2.

Example:

>>> 'sometest'.isalnum()
True
>>> 'some test'.isalnum()
False
>>> 'sometest231'.isalnum()
True
>>> 'sometest%231'.isalnum()
False
>>> '231'.isalnum()
True

Answer 2

You have three problems:

• if a and b == False is not the same is if a == False and b == False ;
• if b == False should be written if not b ; and
• You aren't using str.isalnum , which saves you from the problem anyway.

So it should be:

if not userInput.isalnum():