Check if a string is hexadecimal

Question

I know the easiest way is using a regular expression, but I wonder if there are other ways to do this check.

Why do I need this? I am writing a Python script that re

Answer 1

I know the op mentioned regular expressions, but I wanted to contribute such a solution for completeness' sake:

def is_hex(s):
    return re.fullmatch(r"^[0-9a-fA-F]$", s or "") is not None

Performance

In order to evaluate the performance of the different solutions proposed here, I used Python's timeit module. The input strings are generated randomly for three different lengths, 10, 100, 1000:

s=''.join(random.choice('0123456789abcdef') for _ in range(10))

Levon's solutions:

# int(s, 16)
  10: 0.257451018987922
 100: 0.40081690801889636
1000: 1.8926858339982573

# all(_ in string.hexdigits for _ in s)
  10:  1.2884491360164247
 100: 10.047717947978526
1000: 94.35805322701344

Other answers are variations of these two. Using a regular expression:

# re.fullmatch(r'^[0-9a-fA-F]$', s or '')
  10: 0.725040541990893
 100: 0.7184272820013575
1000: 0.7190397029917222

Picking the right solution thus depends on the length on the input string and whether exceptions can be handled safely. The regular expression certainly handles large strings much faster (and won't throw a ValueError on overflow), but int() is the winner for shorter strings.