How to check if a string only contains certain characters in Python?

You can check if a string only contains certain characters result by using Sets. Declare a set using the characters you want to allow. For example if we want to check if a string only contains 1, 2, 3 and 4, we can use −

Example

from sets import Set
allowed_chars = Set('1234')
validationString = '121'
if Set(validationString).issubset(allowed_chars):
    print True
else:
    print False

Output

This will give you the result −

True

You can also use regexes for the same result. For matching only 1, 2, 3 and 4, we can call the re.match(regex, string) using the regex: "^[1234]+$". 

 example

import re
print(bool(re.match('^[1234]+$', '123abc')))
print(bool(re.match('^[1234]+$', '123')))

Output

False
True

 Keep in mind that regexes have special uses for some characters and hence require escaping them. re.match returns an object, to check if it exists or not, we need to convert it to a boolean using bool().

Rajendra Dharmkar

Published on 08-Dec-2017 16:13:01

• Related Questions & Answers
• Java Program to check if the String contains only certain characters
• How to check if a string contains only decimal characters?
• How to check if a unicode string contains only numeric characters in Python?
• How to check if a Python string contains only digits?
• How to check if a string contains only whitespace letters in Python?
• How to check if a string contains a certain word in C#?
• Python program to check if a string contains all unique characters
• How to check if a string contains only lower case letters in Python?
• How to check if a string contains only upper case letters in Python?
• Check if string contains special characters in Swift
• Check whether the String contains only digit characters in Java
• Check if a string contains only alphabets in Java using Regex
• Check if the String contains only unicode letters in Java
• Is it possible to check if a String only contains ASCII in java?
• Check if a string contains only alphabets in Java using Lambda expression