How to Check if Two Strings Are Equal in Python (With Examples)

Introduction

Python strings equality can be checked using == operator or __eq__() function. Python strings are case sensitive, so these equality check methods are also case sensitive.

Python String equals

Let’s look at some examples to check if two strings are equal or not.

s1 = 'Apple'

s2 = 'Apple'

s3 = 'apple'

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

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

Output:

s1 and s2 are equal.
s1 and s2 are equal.

If you want to perform inequality check, you can use != operator.

if s1 != s3:
    print('s1 and s3 are not equal')

Output: s1 and s3 are not equal

Python String equals case-insensitive check

Sometimes we don’t care about the case while checking if two strings are equal, we can use casefold(), lower() or upper() functions for case-insensitive equality check.

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:

apple
apple
s1 and s3 are equal in case-insensitive comparison
apple
apple
s1 and s3 are equal in case-insensitive comparison
APPLE
APPLE
s1 and s3 are equal in case-insensitive comparison

Python String equals with special characters

Let’s look at some examples where strings contain special characters.

s1 = '$#ç∂'
s2 = '$#ç∂'

print('s1 == s2?', s1 == s2)
print('s1 != s2?', s1 != s2)
print('s1.lower() == s2.lower()?', s1.lower() == s2.lower())
print('s1.upper() == s2.upper()?', s1.upper() == s2.upper())
print('s1.casefold() == s2.casefold()?', s1.casefold() == s2.casefold())

Output:

s1 == s2? True
s1 != s2? False
s1.lower() == s2.lower()? True
s1.upper() == s2.upper()? True
s1.casefold() == s2.casefold()? True

That’s all for checking if two strings are equal or not in Python.

You can checkout complete script and more Python String examples from our GitHub Repository.

== vs .lower() vs .casefold()

The == operator checks for exact equality, including case sensitivity. The .lower() and .casefold() methods, on the other hand, perform case-insensitive comparisons. The difference between the two is that .lower() is not suitable for all Unicode characters, while .casefold() is.

Example:

s1 = 'Apple'
s2 = 'apple'

# Using ==
print(s1 == s2)  # Output: False

# Using .lower()
print(s1.lower() == s2.lower())  # Output: True

# Using .casefold()
print(s1.casefold() == s2.casefold())  # Output: True

When and why to avoid is for strings

The is operator checks for object identity, not equality. It’s important to avoid using is for string comparison, as it can lead to unexpected results. Instead, use the == operator for string comparison.

Example:

s1 = 'Hello'
s2 = 'Hello'

# Using is
print(s1 is s2)  # Output: True, but this checks object identity, not equality

# Using ==
print(s1 == s2)  # Output: True, this checks for equality

Comparison of strings with special characters or Unicode

When comparing strings with special characters or Unicode, it’s important to use the appropriate method for your use case. If you need a case-insensitive comparison, use .casefold(). If you need a case-sensitive comparison, use ==.

Example:

s1 = 'ççç'
s2 = 'ÇÇÇ'

# Case-sensitive comparison using ==
print(s1 == s2)  # Output: False

# Case-insensitive comparison using .casefold()
print(s1.casefold() == s2.casefold())  # Output: True

Common Errors and Debugging

Using is instead of == for string comparison

This is a common mistake when comparing strings in Python. The is operator checks for object identity, not equality. To fix this, use the == operator for string comparison.

Example of the mistake:

s1 = 'Hello'
s2 = 'Hello'
print(s1 is s2)  # This will return True if s1 and s2 refer to the same object, not if they have the same value.

Corrected code:

s1 = 'Hello'
s2 = 'Hello'
print(s1 == s2)  # This will return True if s1 and s2 have the same value.

Comparing string to None or non-string types

When comparing a string to None or non-string types, Python will raise a TypeError. To avoid this, make sure to compare strings to other strings or to None explicitly.

Example of the mistake:

s1 = 'Hello'
s2 = None
print(s1 == s2)  # This will raise a TypeError because s2 is not a string.

Corrected code:

s1 = 'Hello'
s2 = None
if isinstance(s2, str):
    print(s1 == s2)
else:
    print("s2 is not a string.")

Misleading results due to trailing/leading whitespace

Trailing or leading whitespace can lead to misleading results when comparing strings. To fix this, use the strip() method to remove any leading or trailing whitespace before comparing strings.

Example of the mistake:

s1 = 'Hello'
s2 = ' Hello '
print(s1 == s2)  # This will return False because of the leading and trailing whitespace in s2.

Corrected code:

s1 = 'Hello'
s2 = ' Hello '
print(s1 == s2.strip())  # This will return True after removing the leading and trailing whitespace from s2.

FAQs

1. Can you use == for strings in Python?

Yes, you can use the == operator to compare strings in Python. This operator checks if the values of the strings are equal.

Example:

s1 = 'Hello'
s2 = 'Hello'
print(s1 == s2)  # Output: True

2. How do you check if a string is equal in Python?

You can check if a string is equal in Python by using the == operator. This operator checks if the values of the strings are equal.

Example:

s1 = 'Hello'
s2 = 'Hello'
print(s1 == s2)  # Output: True

3. How do you check if a variable is equal to a string in Python?

You can check if a variable is equal to a string in Python by using the == operator. This operator checks if the value of the variable is equal to the string.

Example:

var = 'Hello'
print(var == 'Hello')  # Output: True

4. Do you use == for strings?

Yes, you use the == operator for strings in Python. This operator checks if the values of the strings are equal.

Example:

s1 = 'Hello'
s2 = 'Hello'
print(s1 == s2)  # Output: True

5. How do I check if two strings are equal in Python?

You can check if two strings are equal in Python by using the == operator. This operator checks if the values of the strings are equal.

Example:

s1 = 'Hello'
s2 = 'Hello'
print(s1 == s2)  # Output: True

6. What’s the difference between == and is in Python?

The == operator checks if the values of two objects are equal, while the is operator checks if two objects are the same (i.e., they refer to the same memory location).

Example:

s1 = 'Hello'
s2 = 'Hello'
print(s1 == s2)  # Output: True
print(s1 is s2)  # Output: True, but this checks object identity, not equality

7. How do I do a case-insensitive string comparison in Python?

You can do a case-insensitive string comparison in Python by converting both strings to lowercase or uppercase using the lower() or upper() method, respectively.

Example:

s1 = 'Hello'
s2 = 'hello'
print(s1.lower() == s2.lower())  # Output: True

8. Why is my string comparison not working?

Your string comparison might not be working due to various reasons such as:

• Case sensitivity: Strings are case sensitive, so ‘Hello’ and ‘hello’ are not equal.
• Leading or trailing whitespace: Strings with leading or trailing whitespace are not equal to strings without them.
• Non-string comparison: Comparing a string to a non-string object will raise a TypeError.

Example:

s1 = 'Hello'
s2 = 'hello'
print(s1 == s2)  # Output: False, due to case sensitivity

9. Can I compare a string to None in Python?

Yes, you can compare a string to None in Python. However, you should ensure that the object you are comparing is a string or None explicitly to avoid TypeError.

Example:

s1 = 'Hello'
s2 = None
if isinstance(s2, str):
    print(s1 == s2)
else:
    print("s2 is not a string.")

10. How to compare multi-line strings in Python?

You can compare multi-line strings in Python by using the == operator. However, ensure that the strings are formatted correctly, including any newline characters.

Example:

s1 = """Hello
World"""
s2 = """Hello
World"""
print(s1 == s2)  # Output: True

Conclusion

In this comprehensive guide, we have delved into the intricacies of string comparison in Python. We began by exploring the fundamental methods for checking string equality, including the use of the == operator and the __eq__() function. We also highlighted the importance of considering case sensitivity in string comparisons and demonstrated how to perform case-insensitive comparisons using the lower(), upper(), and casefold() methods.

Furthermore, we discussed the key differences between the == operator and the is operator, emphasizing the importance of using == for string comparison to ensure accurate results. Additionally, we touched upon common errors that can occur during string comparison, such as ignoring case sensitivity or comparing strings to non-string objects, and provided valuable debugging tips to overcome these issues.

To further enhance your understanding of string manipulation in Python, we recommend exploring the following tutorials:

• Python String Comparison: Learn more about the nuances of string comparison in Python, including how to handle case sensitivity and Unicode characters.
• Python String Functions: Discover the various string functions available in Python, including methods for string manipulation, formatting, and more.
• An Introduction to Working with Strings in Python 3: Get started with the basics of working with strings in Python 3, including string literals, indexing, and slicing.
• Python: Find String in List: Learn how to search for a string within a list of strings in Python, including methods for exact and partial matches.

By reading these tutorials, you’ll gain a deeper understanding of string manipulation and comparison in Python, enabling you to write more efficient and effective code.