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

Simple solution in case you need a pattern to validate prefixed hex or binary along with decimal

\b(0x[\da-fA-F]+|[\d]+|0b[01]+)\b

Sample: https://regex101.com/r/cN4yW7/14

Then doing int('0x00480065006C006C006F00200077006F0072006C00640021', 0) in python gives 6896377547970387516320582441726837832153446723333914657

The base 0 invokes prefix guessing behaviour. This has saved me a lot of hassle. Hope it helps!

Answer 2

One more simple and short solution based on transformation of string to set and checking for subset (doesn't check for '0x' prefix):

import string
def is_hex_str(s):
    return set(s).issubset(string.hexdigits)

More information here.

Answer 3

This will cover the case if the string starts with '0x' or '0X': [0x|0X][0-9a-fA-F]

d='0X12a'
all(c in 'xX' + string.hexdigits for c in d)
True

Answer 4

In Python3, I tried:

def is_hex(s):
    try:
        tmp=bytes.fromhex(hex_data).decode('utf-8')
        return ''.join([i for i in tmp if i.isprintable()])
    except ValueError:
        return ''

It should be better than the way: int(x, 16)

Answer 5

Most of the solutions proposed above do not take into account that any decimal integer may be also decoded as hex because decimal digits set is a subset of hex digits set. So Python will happily take 123 and assume it's 0123 hex:

>>> int('123',16)
291

This may sound obvious but in most cases you'll be looking for something that was actually hex-encoded, e.g. a hash and not anything that can be hex-decoded. So probably a more robust solution should also check for an even length of the hex string:

In [1]: def is_hex(s):
   ...:     try:
   ...:         int(s, 16)
   ...:     except ValueError:
   ...:         return False
   ...:     return len(s) % 2 == 0
   ...: 

In [2]: is_hex('123')
Out[2]: False

In [3]: is_hex('f123')
Out[3]: True

Answer 6

Another option:

def is_hex(s):
    hex_digits = set("0123456789abcdef")
    for char in s:
        if not (char in hex_digits):
            return False
    return True