How to check if a string contains letters or letters and an apostrophe but NO numbers?

Question

I'm trying to find out if there's a simple means using for loops and lists to check if a user input string contains letters or letters and an apostrophe, but not numbers or letters and numbers (letters and numbers and an apostrophe)?

I have tried numerous methods and cannot seem to figure it out? I'd appreciate any leads! Thanks.

Not clear precisely what you're looking for. Sounds like you only want strings with no numerical digits, is that correct? — Larry Lustig, Nov 18 '15 at 21:42
I am not sure, I've understood what you are asking but check this maybe? [Checking whether a variable is an integer or not](http://stackoverflow.com/questions/3501382/checking-whether-a-variable-is-an-integer-or-not) — Lafexlos, Nov 18 '15 at 21:42
Does `isalpha` return False if punctuation is in the string? I'm on mobile and can't test. — tblznbits, Nov 18 '15 at 21:45

score 2 · Answer 1 · answered Nov 18 '15 at 21:52

You seem to want only strings that contain letters (plus maybe an apostrophe), but no numbers, though you have expressed the requirements more verbosely. This can be accomplished without regexes as follows:

not any(c for c in my_str if c not in string.ascii_letters + "'")

See the following example code:

>>> test = ['abcde', "abcde'", 'abcde123', "abcde'123", 'abcde.']
>>> for s in test:
...   print(s, '-->', not any(c for c in s if c not in string.ascii_letters + "'"))
... 
abcde --> True
abcde' --> True
abcde123 --> False
abcde'123 --> False
abcde. --> False

Hopefully it's obvious that it would be more efficient to do the string.ascii_letters + "'" only once, and that you must import string first. This is just an example.

score 1 · Answer 2 · answered Nov 20 '15 at 21:34

You can also use set.issuperset specifying a set of allowed characters:

from string import ascii_letters
allowed = set(ascii_letters+"'")
test = ['abcde', "abcde'", 'abcde123', "abcde'123", 'abcde.']
for s in test:
   print("{} {}".format(s, allowed.issuperset(s)))

Output:

abcde True
abcde' True
abcde123 False
abcde'123 False
abcde. False

How to check if a string contains letters or letters and an apostrophe but NO numbers?

2 Answers2