Python - How To Compare Strings in Python

ID : 98

viewed : 97

Tags : PythonPython String

vote vote

99

This tutorial will introduce how to compare strings in Python.

Use the Relational Operators to Compare Strings in Python

In Python, the relational operators are used to compare different values. Strings can be compared using these operators. When we compare strings, we compare their Unicode values.

In the code below, we will compare two strings using the relational operators and print their results.

str1 = 'Mark' str2 = 'Jack'  print(str1>str2) print(str1<str2) print(str1==str2) print(str1!=str2) print(str1>=str2) print(str1<=str2) 

Output:

True False False True True False 

String comparisons in Python are case-sensitive. In case we want to do the string comparisons in a case-insensitive way, we can use the islower() function, which converts all the characters in the string to lower case, and then proceed to compare them.

Use the is Operator to Compare Strings in Python

The is operator is used to check for identity comparison in Python. This means that if two variables have the same memory location, then their identity is considered the same, and the result of their comparison is True; otherwise, it is False. The is operator is different from the == relational operator since the latter tests for equality. For example,

str1 = 'Mark' str2 = str1 str3 = 'MARK' print(str1 is str2) print(str1 is str3) 

Output:

True False  

Use the User-Defined Logic to Compare Strings in Python

Besides these built-in operators, we can create our user-defined functions to compare strings on other factors like their length and more.

In the following code, we implement a user-defined function to compare the length of two strings.

def check_len(s1,s2):     a = len(s1)     b = len(s2)     if (a>b):         print(s1, " is Longer")     elif (a == b):         print("Equal Length")     else:         print(s2, " is Longer")  str1 = 'Mark' str2 = 'Jack' check_len(str1,str2) 

Output:

Equal Length 

Use the Regular Expressions to Compare Strings in Python

Regular Expressions are very heavily used in Python and can be used to check if a string matches a pattern or not.

In the following example, we will compare two strings with a pattern using regular expressions.

import re str1 = 'Mark' str2 = 'Jack'  def check_pattern(s):     if re.match("Ma[a-z]+",s):         print("Pass")     else:         print("Fail")  check_pattern(str1) check_pattern(str2) 

Output:

True False 

The re pattern in the above checks if a string starts with Ma and is followed by other letters. That is why Mark returns True, and ack returns False.

  • Related HOW TO?