How to check that a string contains only “a-z”, “A-Z” and “0-9” characters [duplicate]

Question

I am importing string and trying to check if text contains only "a-z", "A-Z", and "0-9".

But I get only input and it doesn't print success when I enter letters and digits

import string
text=input("Enter: ")
correct = string.ascii_letters + string.digits
if text in correct:
    print("Success")

Answer 1

You could use regex for this, e.g. check string against following pattern:

import re
pattern = re.compile("[A-Za-z0-9]+")
pattern.fullmatch(string)

Explanation:

[A-Za-z0-9] matches a character in the range of A-Z, a-z and 0-9, so letters and numbers.

+ means to match 1 or more of the preceeding token.

The re.fullmatch() method allows to check if the whole string matches the regular expression pattern. Returns a corresponding match object if match found, else returns None if the string does not match the pattern.

All together:

import re

if __name__ == '__main__':
    string = "YourString123"
    pattern = re.compile("[A-Za-z0-9]+")

    # if found match (entire string matches pattern)
    if pattern.fullmatch(string) is not None:
        print("Found match: " + string)
    else:
        # if not found match
        print("No match")