# Python Program to check if String contains only Defined Characters using Regex

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When it is required to check if a given string contains specific characters using regular expression, a regular expression pattern is defined, and the string is subjected to follow this pattern.

## Example

Below is a demonstration of the same

import re
def check_string(my_string, regex_pattern):

if re.search(regex_pattern, my_string):
print("The string contains the defined characters only")
else:
print("The doesnot string contain the defined characters")

regex_pattern = re.compile('^[Python]+\$')

my_string_1 = 'Python'
print("The string is :")
print(my_string_1)
check_string(my_string_1 , regex_pattern)

my_string_2 = 'PythonInterpreter'
print("\nThe string is :")
print(my_string_2)
check_string(my_string_2, regex_pattern)

## Output

The string is :
Python
The string contains the defined characters
The string is :
PythonInterpreter
The doesn’t string contain the defined characters

## Explanation

• The required packages are imported.

• A method named ‘check_string’ is defined, and it takes the string and a regular expression as parameters.

• The ‘search’ method is called and checked to see if a specific set of characters is present in the string.

• Outside the method, the ‘compile’ method is called on the regular expression.

• The string is defined and is displayed on the console.

• The method is called by passing this string.

• The output is displayed on the console.

Updated on 20-Sep-2021 10:43:00