Python check if string contains char

How to Check if a String Contains Special Characters in Python

Here, we will develop Programs for How to check if a string contains special characters in Python. A special character is a character that is not an alphabetic or numeric character. Non-alphabetic or non-numeric character, such as @, #, $, %, &, * and +. We are going to write a program that checks whether a string contains any special character or not using various methods.

How to Check Special Characters in Python

We will first import the required package from the Python library and take a string while declaring the variables. Then, check the presence of special characters and pass it into the search function. The search function matches all the characters of the string to the set of special characters. If there is a match then it returns the matched character otherwise it will return None.

# Python program to check special character # import required package import re # take inputs string = input('Enter any string: ') # special characters special_char = re.compile('[@_!#$%^&*()<>?/\|><~:]') # check string contains special characters or not if(special_char.search(string) == None): print('String does not contain any special characters.') else: print('The string contains special characters.')

Enter any string: @knowprogram
The string contains special characters.

Enter any string: Know Program
String does not contain any special characters.

Enter any string: $25
The string contains special characters.

How to Identify Special Characters in Python

We are using the re.match() function to check whether a string contains any special character or not. The re.match() method returns a match when all characters in the string are matched with the pattern and None if it’s not matched.

# Python program to check special character # import required package import re # take inputs string = input('Enter any string: ') # check string contains special characters or not if(bool(re.match('^[a-zA-Z0-9]*$', string)) == True): print('String does not contain any special characters.') else: print('The string contains special characters.')

Enter any string: [email protected]The string contains special characters.

How to Check if a String Contains Special Characters in Python

In the above program, we used the re.match() method but in this program, we are using the re.search() method. This is also a function in the RegEx module. The re.search() function locates a match anywhere in the string.

# Python program to check special character # import required package import re # take inputs string = input('Enter any string: ') # check string contains special characters or not if(bool(re.search('^[a-zA-Z0-9]*$', string)) == True): print('String does not contain any special characters.') else: print('The string contains special characters.')

Enter any string: Python
String does not contain any special characters.

Function to Check Special Characters in Python

Function to check special Characters. The string.punctuation is pre-defined in the string module of Python3. It contains all the characters as a string. This returns all sets of punctuation.

# Python program to check special character # importing string function import string # take inputs ch = input('Enter any string: ') # special characters invalid_char = set(string.punctuation) # check string contains special characters or not if any(char in invalid_char for char in ch): print('String does not contain any special characters.') else: print('The string contains special characters.')

Enter any string: string.punctuation
The string contains special characters.

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Check if String Contains Specific Characters in Python

In this article, we will learn how to check a string for specific characters in Python.

Table Of Contents

Method 1: Using in operator

We can use the in operator to check if a particular character exists in a given string or not. If it exists, the True is returned, otherwise False is returned. Let’s see some examples

In this example, we will consider the string – “Welcome to thisPointer” and check for the character – ‘t’ in it.

Frequently Asked:

strValue = "Welcome to thisPointer" print("String - ", strValue) # Check for 't' in string strValue if 't' in strValue: print("Character 't' exists in the String") else: print("Character 't' does not exists in the String")

String - Welcome to thisPointer Character 't' exists in the String

We can see that character – ‘t’ is found in strValue.

In this example, we will consider the string – “Welcome to thisPointer” and check the existence of multiple characters in it. For ir, we will iterate over all characters in list, and for each character, check if it exists in the string or not. For example,

strValue = "Welcome to thisPointer" print("String - ", strValue) # List of characters listOfCharacters = ['W','e','P','Y'] # Check if characters in the list exists in the above string or not for ch in listOfCharacters: # Check if character ch exists in string strValue if ch in strValue: print("Character \"", ch, "\" exists in the String") else: print("Character \"", ch, "\" does not exists in the String")

String - Welcome to thisPointer Character " W " exists in the String Character " e " exists in the String Character " P " exists in the String Character " Y " does not exists in the String

We can see that characters – ‘W’,’e’ and ‘P’ were found in string strValue, but character ‘Y’ was not found in the string.

Method 2: Using contains() method

The contains() method of string class, checks if a particular character exists in the given string or not. If it exists, True is returned, otherwise False is returned.

In this example, we will consider the string – “Welcome to thisPointer” and check for the character – ‘t’ in it.

strValue = "Welcome to thisPointer" print("String - ", strValue) # A character that need to checked ch = 't' # Check if character ch exists in string strValue if strValue.__contains__(ch): print("Character \"", ch, "\" exists in the String") else: print("Character \"", ch, "\" does not exists in the String")

String - Welcome to thisPointer Character " t " exists in the String

We can see that character – ‘t’ exists in the string.

In this example, we will consider the string – “Welcome to thisPointer” and check the existence of particular characters.

strValue = "Welcome to thisPointer" print("String - ", strValue) # List of characters listOfCharacters = ['W','e','P','Y'] # Check if characters in the list exists in the above string or not for ch in listOfCharacters: # Check if character ch exists in string strValue if strValue.__contains__(ch): print("Character \"", ch, "\" exists in the String") else: print("Character \"", ch, "\" does not exists in the String")

String - Welcome to thisPointer Character " W " exists in the String Character " e " exists in the String Character " P " exists in the String Character " Y " does not exists in the String

We can see that characters – ‘W’,’e’ and ‘P’ are found in string, but the character ‘Y’ is not found in the string.

Method 2: Using find() method

The string class provides a member function find(). It accepts a string or a character as an argument, and returns the lowest index of the given string/character in the calling string object. If string/character does not exists in the calling string object, then it returns -1.

We can use this to check if a character exists in a string or not. For that, we just need to pass the character in find() function, and check if returned value is not -1. Let’s see some examples,

In this example, we will consider the string – “Welcome to thisPointer” and check for the character – ‘t’ in it.

strValue = "Welcome to thisPointer" print("String - ", strValue) # A character that need to be serached ch = 't' # Check if character ch exists in string strValue if strValue.find(ch) != -1: print("Character \"", ch, "\" exists in the String") else: print("Character \"", ch, "\" does not exists in the String")

String - Welcome to thisPointer Character " t " exists in the String

We can see that character – ‘t’ is found in string1.

In this example, we will consider the string – “Welcome to thisPointer” and check the existence of particular characters.

strValue = "Welcome to thisPointer" print("String - ", strValue) # List of characters listOfCharacters = ['W','e','P','Y'] # Check if characters in the list exists in the above string or not for ch in listOfCharacters: # Check if character ch exists in string strValue if strValue.find(ch) != -1: print("Character \"", ch, "\" exists in the String") else: print("Character \"", ch, "\" does not exists in the String")

String - Welcome to thisPointer Character " W " exists in the String Character " e " exists in the String Character " P " exists in the String Character " Y " does not exists in the String

We can see that characters – ‘W’,’e’ and ‘P’ exists in the string, but the character ‘Y’ is not found in the string.

Summary

We learned to check a string for specific character/characters using three different techniques. Thanks.

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