How to Check for Special Characters in Python

Checking for special characters in a Python string can add robustness to your code especially if you are dealing with user input data. Special characters can include punctuation, special symbols, whitespace, etc., and it’s common to require certain restrictions on these when processing text data.

This tutorial will guide you on how to check for special characters in a string using Python.

Step 1: Create Your String

Firstly, we need to define the string in which we want to check for special characters. Use the code snippet below to create a string.

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text = "Hello, World!$"

Step 2: Use Regular Expressions

The Python re module provides support for regular expressions or RegEx. This is incredibly useful for pattern matching with strings. Import it using the following code:

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import re

Let’s define a function that uses the .findall method in Python’s re module. The re.findall() method returns all non-overlapping matches of pattern in string, as a list of strings.

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def check_special_char(string):
  special_char_regex = re.compile('[@_!#$%^&*()<>?/\|}{~:]')
  if(special_char_regex.search(string) == None):
    return False
  else:
    return True

Step 3: Running the Function

Lastly, let’s use our function check_special_char to check if there are special characters in the text and print the output.

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print(check_special_char(text))

The function will return True if the string contains a special character and False if it doesn’t.

True

The Full Code

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import re
 
text = "Hello, World!$"
 
def check_special_char(string):
  special_char_regex = re.compile('[@_!#$%^&*()<>?/\|}{~:]')
  if(special_char_regex.search(string) == None):
    return False
  else:
    return True
 
print(check_special_char(text))

Conclusion

Hopefully, this tutorial has given you a clear understanding of how to check for special characters in a Python string using regular expressions. Regular expressions are a powerful tool that can greatly enhance your text-processing capabilities in Python.

Remember, practice is key to mastering any new concept, so try incorporating these techniques into your own Python projects to familiarize yourself with them.