Python Regex Match Special Characters

Question

I need a function that can test whether a string has any special characters in it. I'm currently using the following function with no luck:

import re

def no_special_characters(s, pat=re.compile('[@_!#$%^&*()<>?/\|}{~:]')):
  if pat.match(s):
    print(s + " has special characters")
  else:
    print(s + " has NO special characters")

I get the following results:

no_special_characters('$@')  # $@ has special characters
no_special_characters('a$@') # a$@ has NO special characters
no_special_characters('$@a') # $@a has special characters

This doesn't make any sense to me. How can I test for ANY special characters in a string?

`re.match` matches the string *from the start*. `re.search` matches in any position. `re.fullmatch` matches the whole string — Giacomo Alzetta, Aug 29 '19 at 16:02
You can add `.*` to the start and end of your regex but whether that is the right approach is up for debate. — MonkeyZeus, Aug 29 '19 at 16:02

score 4 · Accepted Answer · answered Aug 29 '19 at 16:01

The problem with using match() here is that it is anchored to the beginning of the string. You want to find a single special character anywhere in the string, so use search() instead:

def no_special_characters(s, pat=re.compile('[@_!#$%^&*()<>?/\|}{~:]')):
    if pat.search(s):
        print(s + " has special characters")
    else:
        print(s + " has NO special characters")

You could also keep using match() with the following regex pattern:

.*[@_!#$%^&*()<>?/\|}{~:].*

score 0 · Answer 2 · answered Aug 29 '19 at 16:04

0

Use search function instead of match function.

answered Aug 29 '19 at 16:04

Usman

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Hey, just a heads up, the python 3.x tag is for questions about behaviour specific to python 3 – c2huc2hu Aug 29 '19 at 18:49

Python Regex Match Special Characters

2 Answers2