How to Compare String in Python? [With Examples]

String comparison is an essential operation in Python programming. It permits us to compare two strings and define their relative order, equality, and other factors. Whether you’re sorting a list of names or exploring for specific substrings, string comparison is an important tool in your programming arsenal. In this article, we will explore different methods and operators for comparing strings in Python, along with their use cases and samples.In this article, we have studied various methods and operators for comparing strings in Python.

What are Strings?

A string is a series of characters, representing letters, numbers, or symbols. A character is the building block of a string. It could be a note, a number, or a symbol. For example, in the English Language, we have 26 alphabets known, each of which is an alphabet. But the computer system does not comprehend characters and hence it deals with binary numbers. All the characters that we notice on our screen are internally stored and manipulated as a combination of 0s and 1s.

The conversion of symbols and binary numbers is called encoding, and the reverse of this is known as decoding.  Some of the famous encodings are ASCII and Unicode. So, we can determine a string as a sequence of Unicode characters, or in layman’s terms, a combination of alphabets, numbers, or symbols that are confined between two quotation marks.

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What is String Comparison?

String comparison is the procedure of comparing two strings to define their relative order, equality, or other characteristics. Python delivers various methods and operators that allow us to perform string comparisons efficiently. By comparing the characters in each string, we can ascertain their similitudes, differences, or order in lexicographical (alphabetical) terms.

Comparing strings is essential to check if two strings are the same or not. We can utilize it to verify if two strings are equal and perform a specific task only if they are equal. It is very necessary for search functionality.

Importance of String Comparison

String comparison is widely operated in programming for tasks such as searching, sorting, conditional branching, and more. It plays a vital role in applications ranging from data processing to natural language processing. Understanding the various methods and operators available for string comparison is necessary for writing effective and efficient Python code.

Let us say you made a student database for a university. If you desired to access the records of a particular student you would have to search for them in the database. To confirm that the record you discovered is the one you wanted, you would have to match the name of the record with the name you had in sense.

In such plans, you are required to compare two strings. Similarly for situations like checking for a valid email address, checking the name that exists in a record, etc; we need string comparisons.

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Python String Comparison Operators

In Python language, we can compare two strings such as determining whether the two strings are equivalent to each other or not, or even which string is more significant or smaller than each other. Let us check some of the string comparison operators employed for this purpose below:

• ==: This operator inspects whether two strings are equal.
• !=: This operator inspects whether two strings are not equal.
• <: This operator inspects whether the string on the left side is smaller than the string on the right side.
• <=: This operator inspects whether the string on the left side is smaller or equal to the string on the right side.
• >: This operator inspects whether the string on the left side is greater than the string on the right side.
• >=: This operator inspects whether the string on the left side is greater than the string on the right side.

Let us take an example to comprehend these operators:

string1 = "Abrar"
string2 = "Ahmed"
string3 = "ABCD"
string4 = "ABCD"
if string1 <= string2:
    print(string1," is smaller ",string2," is greater")
if string2 >= string4:
    print(string4," is smaller ", string2," is greater")
if string3 == string4:
    print(string3," is equal to ",string4)
if string1 != string3:
    print(string1," is not equal to ", string3)

Output:

Abrar  is smaller  Ahmed  is greater
ABCD  is smaller  Ahmed  is greater
ABCD  is equal to  ABCD
Abrar  is not equal to  ABCD

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String Equals Check in Python

In Python, we can review whether strings are equal or not using two ways. The first way is to use the relational equality operator “==” to perform the string comparison.

The second way is to use a dedicated string function to perform comparisons, the __eq__() function. It is a magic function described in the string class and compares two strings to return True if they are equal or Fale if they are not.

Example:

s1 = 'String'
s2 = 'String'
s3 = 'string'

# case sensitive equals check
if s1 == s2:
    print('s1 and s2 are equal.')

if s1.__eq__(s2):
    print('s1 and s2 are equal.')

Here, we check strings s1 and s2 whether are equal or not and then utilize the “if” conditional statement with a combination of the equal operator.

Output:

s1 and s2 are equal.

 s1 and s2 are equal.

String Comparison Using the ‘is’ Operator

In Python, the is operator is utilized to determine if two objects are the same object in memory. The is operator compares the memory addresses of the objects instead of their values. While the is operator is not generally used for string comparison, it can be helpful in specific cases.

Let’s comprehend it better with an example:

string1 = "favtutor"
string2 = "favtutor"
string3 = "Favtutor"

if string1 is string2:
    print("The strings are same.")
else:
    print("The strings are different.")
    
if string1 is string3:
    print("The strings are same.")
else:
    print("The strings are different.")

Output:

The strings are same.
The strings are different.

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In this instance, both string1 and string2 guide to the same string object because Python internally caches and reuses some strings as an optimization. As a result, the output is “The strings are the same”.

Case Sensitivity in String Comparisons

While reviewing the equality in strings sometimes we expect to ignore the case of the string while comparing. This can be done by bringing both the strings that we expect to compare in one particular case, ie, we could make both the strings uppercase or lowercase and then complete the comparison.

The cases of the strings can be modified with the aid of three in-built functions, casefold(), upper(), and lower(). Both casefold() and lower() processes convert the string to lowercase.

But the distinction is casefold() is more assertive and can convert more letters to lowercase than lower(). The upper() process can be used to convert all the characters in the string to uppercase.

s1 = 'String'
s2 = 'String'
s3 = 'string'

if s1.casefold() == s3.casefold():
    print(s1.casefold())
    print(s3.casefold())
    print('s1 and s3 are equal in case-insensitive comparison')

if s1.lower() == s3.lower():
    print(s1.lower())
    print(s3.lower())
    print('s1 and s3 are equal in case-insensitive comparison')

if s1.upper() == s3.upper():
    print(s1.upper())
    print(s3.upper())
    print('s1 and s3 are equal in case-insensitive comparison')

Output:

string

 string

 s1 and s3 are equal in case-insensitive comparison

 string

 string

 s1 and s3 are equal in case-insensitive comparison

 STRING

 STRING

 s1 and s3 are equal in case-insensitive comparison

String comparison can be done whether the case is liable or not. For case-sensitive comparisons, we utilize the equality operator or the __eq__() function. For case-insensitive comparisons, we can modify all the characters in the string to lowercase using casefold() or lower() methods.

We could also convert all the characters to upper case using the upper() process.

Best Practices for String Comparison

When executing string comparisons in Python, it’s important to follow the most useful practices to ensure proper and efficient comparisons. Here are some tips to keep in mind:

• Use the right operator or method based on your specific comparison requirements. For instance, the equality operator (==) is typically used for general string equality checks, while the relational operators (<, >, <=, >=) are utilized for lexicographical comparisons.
  
• Consider case sensitivity when comparing strings. By default, string comparison in Python is case-sensitive. If you require to perform a case-insensitive comparison, convert both strings to the same case (e.g., lowercase or uppercase) before comparing them.
  
• Be aware of the Unicode values of characters when performing lexicographical comparisons. Python compares characters founded on their Unicode values, which may result in unexpected outcomes if you’re not conscious of the underlying character encoding.
  
• Utilize user-defined functions when you are required to customize the comparison logic based on specific criteria or conditions. User-defined functions deliver flexibility and allow you to take complex string comparison scenarios.
  
• Consider using additional modules, such as difflib, when you require advanced string comparison algorithms or methods. These modules can deliver specialized functionality and enhance the accuracy or efficiency of your comparisons.

Applications of String Comparison

Following are some of the use cases of string comparison:

•  Searching and Matching: String comparison lets you to search for specific substrings within a larger string. By comparing the target substring with various parts of the input string, you can identify matching patterns or sequences.
• Sorting: When you require to sort a list of strings, string comparison is important for determining their order. By comparing strings lexicographically, you can place them in ascending or descending order.
•  Authentication and Validation: String comparison is frequently used for authentication goals, such as comparing user input with stored passwords or validating input against predefined patterns or formats.
•  Conditional Branching: String comparison is often used in dependent statements, such as if-else and switch statements. By comparing strings, you can manage the flow of your program and execute other code blocks based on distinct conditions.
•  Natural Language Processing: String comparison methods play a important role in natural language processing tasks, such as sentiment analysis,text classification, and information recovery. By comparing strings, you can determine similarities or differences between texts and extract meaningful insights.
•  Data Processing and Analysis: String comparison is helpful in data processing and analysis tasks, such as data cleaning, deduplication, and data integration. By comparing strings, you can determine duplicate records or match identical data from different sources.

Conclusion

String comparison is a basic operation in Python programming, with applications ranging from sorting and searching to authentication and data processing. In this article, we have studied various methods and operators for comparing strings in Python. We have understood about equality and inequality operators, relational operators, best practises, and utilize cases for string comparison.