Check if one character in string is numeric or is a letter [Python]

Question

I want to check the string and see if at least one of the characters in the string is a letter or number. How would i do this?

Answer 1

You could use re.search

if re.search(r'[a-zA-Z\d]', string):

It will return a match object if the string contain at-least a letter or a digit.

Example:

>>> s = "foo0?"
>>> re.search(r'[a-zA-Z\d]', s)
<_sre.SRE_Match object; span=(0, 1), match='f'>
>>> s = "???"
>>> re.search(r'[a-zA-Z\d]', s)
>>> s = "???0"
>>> re.search(r'[a-zA-Z\d]', s)
<_sre.SRE_Match object; span=(3, 4), match='0'>
>>> 

Answer 2

str.isalnum:

In [16]: s = "foo"    
In [17]: s.isalnum()
Out[17]: True
In [20]: s = "123"
In [21]: s.isalnum()
Out[21]: True
In [22]: s = "foo123"
In [23]: s.isalnum()
Out[23]: True

Then use any:

any(x.isalnum() for x in  s)

In [24]: s = "!@1"   
In [25]: any(x.isalnum() for x in  s)
Out[25]: True
In [27]: s = "!@()"
In [28]: any(x.isalnum() for x in  s)
Out[28]: False

It will short circuit if we find any alpha or numeric character or return False if the string contains neither.

Answer 3

Another solution might be (don't forget to import string):

any(c in s for c in string.letters + string.digits)

(In contrast to the regex solution this is locale-dependent, e.g. including German umlauts etc.)