How to Check if Two Strings are Anagrams in Python 🐍

An anagram is a word or phrase formed by rearranging the letters of another, using all original letters exactly once. For example, “listen” and “silent” are anagrams. Checking if two strings are anagrams is a common task in programming, and Python offers several simple ways to accomplish this.

In this blog post, we’ll explore multiple methods for checking if two strings are anagrams.

What is an Anagram?

An anagram of a string uses all the original letters exactly once and simply rearranges them. To be anagrams, two strings must:

Contain the same characters
Have the same frequency of each character

Method 1: Sorting the Strings

The easiest way to check if two strings are anagrams is to sort their characters. If the sorted versions of both strings match, they are anagrams.

Code Example:

# Program to check if two strings are anagrams by sorting

# Step 1: Define a function to check for anagrams
def are_anagrams(str1, str2):
    # Step 2: Sort and compare the strings
    return sorted(str1) == sorted(str2)

# Step 3: Test the function
string1 = "listen"
string2 = "silent"
print(f"Are '{string1}' and '{string2}' anagrams? {are_anagrams(string1, string2)}")

Explanation:

Sorting the Strings: sorted(str1) and sorted(str2) return lists of sorted characters for each string.
Comparison: If these sorted lists are equal, the strings are anagrams.

Output:

Are 'listen' and 'silent' anagrams? True

Method 2: Using `Counter` from `collections`

Using Counter from Python’s collections module lets us count the frequency of each character and then compare the counts.

Code Example:

# Program to check if two strings are anagrams using Counter

from collections import Counter

# Step 1: Define a function to check for anagrams
def are_anagrams(str1, str2):
    # Step 2: Count the characters and compare the counts
    return Counter(str1) == Counter(str2)

# Step 3: Test the function
string1 = "triangle"
string2 = "integral"
print(f"Are '{string1}' and '{string2}' anagrams? {are_anagrams(string1, string2)}")

Explanation:

Counter: Counter(str1) and Counter(str2) count each character in the strings.
Comparison: If both counters are equal, the strings are anagrams.

Output:

Are 'triangle' and 'integral' anagrams? True

Method 3: Using Character Frequency Count

We can manually check if two strings are anagrams by counting each character’s occurrence and comparing these counts.

Code Example:

# Program to check if two strings are anagrams using character frequency count

# Step 1: Define a function to check for anagrams
def are_anagrams(str1, str2):
    # Step 2: Check if lengths are equal (early exit if not)
    if len(str1) != len(str2):
        return False

    # Step 3: Create dictionaries for character frequencies
    count1 = {}
    count2 = {}

    # Step 4: Count characters in each string
    for char in str1:
        count1[char] = count1.get(char, 0) + 1
    for char in str2:
        count2[char] = count2.get(char, 0) + 1

    # Step 5: Compare frequency dictionaries
    return count1 == count2

# Step 6: Test the function
string1 = "heart"
string2 = "earth"
print(f"Are '{string1}' and '{string2}' anagrams? {are_anagrams(string1, string2)}")

Explanation:

Length Check: If the strings don’t have the same length, they aren’t anagrams.
Frequency Dictionaries: count1 and count2 store character counts for each string.
Comparison: If the frequency dictionaries are equal, the strings are anagrams.

Output:

Are 'heart' and 'earth' anagrams? True

Method 4: Using `defaultdict` for Character Counting

Using defaultdict from Python’s collections module provides an efficient way to handle character counts without manual initialization.

Code Example:

# Program to check if two strings are anagrams using defaultdict

from collections import defaultdict

# Step 1: Define a function to check for anagrams
def are_anagrams(str1, str2):
    # Step 2: Check if lengths are equal (early exit if not)
    if len(str1) != len(str2):
        return False

    # Step 3: Create a defaultdict for character frequency
    count = defaultdict(int)

    # Step 4: Count characters in the first string
    for char in str1:
        count[char] += 1

    # Step 5: Subtract counts using the second string
    for char in str2:
        count[char] -= 1
        if count[char] < 0:
            return False

    # Step 6: If all values are zero, they are anagrams
    return all(value == 0 for value in count.values())

# Step 7: Test the function
string1 = "dusty"
string2 = "study"
print(f"Are '{string1}' and '{string2}' anagrams? {are_anagrams(string1, string2)}")

Explanation:

Defaultdict for Counting: defaultdict(int) initializes counts at zero.
Subtract Counts: We increase counts for str1 and decrease for str2.
All Zeros Check: If all counts are zero, the strings are anagrams.

Output:

Are 'dusty' and 'study' anagrams? True

Conclusion

In this blog, we explored four methods for checking if two strings are anagrams:

Sorting: Simple and easy-to-read.
Counter from collections: Fast and efficient.
Manual Frequency Count: A straightforward counting approach.
defaultdict: Streamlined counting with auto-initialization.

Each method has its strengths and may be suitable for different scenarios. Choose the one that fits your needs best, and happy coding! 😊

Stay tuned for more Python programming tutorials and tips!

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