🐍 10 Essential String Operations in Python (With Examples & Output)

 

Working with strings is one of the most common tasks in programming. Whether you're preparing for coding interviews or brushing up on Python basics, mastering string operations is a must.

Here are 10 essential string problems solved in Python, along with clear explanations and example outputs.

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✅ 1. Reverse a String

str1='shami'
rev_str=str1[::-1]
print(rev_str)   

Explanation:
Using Python’s slicing feature [::-1], we reverse the string.

Output:

imahs

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✅ 2. Check if Two Strings Are Anagrams

def are_anagrams(s1, s2): 
    return sorted(s1)==sorted(s2)
print(are_anagrams("listen","silent"))  

Explanation:
Two strings are anagrams if they have the same characters in any order. Sorting helps compare them.

Output:

True

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✅ 3. Find the First Non-Repeating Character in a String

def non_repating_str(s):
    for char in s:
        if s.count(char)==1:
            return char
print(non_repating_str("aabbssdhsmi"))

Explanation:
The loop checks each character’s count. The first character with count 1 is returned.

Output:

d

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✅ 4. Count the Frequency of Each Character

s = "hello world"
freq = {}

for ch in s:
    freq[ch] = freq.get(ch, 0) + 1

print(freq)

Explanation:
Using a dictionary, we count how many times each character appears.

Output:

{'h': 1, 'e': 1, 'l': 3, 'o': 2, ' ': 1, 'w': 1, 'r': 1, 'd': 1}

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✅ 5. Remove All Vowels from a String

def remove_vowels(str4):
    vowels = "aeiouAEIOU"
    result = ""
    for char in str4:
        if char not in vowels:
            result += char
    return result
print(remove_vowels("Mohd Shami"))

Explanation:
We iterate through the string and skip vowels.

Output:

Mhd Shm

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✅ 6. Replace a Substring in a String

str5 = "Shami is a great player"
str6 = "Sammy"

result = str5.replace("Shami", str6)
print(result)

Explanation:
Using .replace(), we substitute "Shami" with "Sammy".

Output:

Sammy is a great player

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✅ 7. Check if a String is a Valid Palindrome

str7="shami"
str8="imahs"
str9=str8[::-1]
if str8==str9:
    print("The strings are plindrome.")
else:
    print("The strings are not plindrome.")

Explanation:
The code checks if str8 is equal to its reverse. Small typo: "plindrome" should be "palindrome".

Output:

The strings are not plindrome.

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✅ 8. Find the Longest Substring Without Repeating Characters

s = "abcabcbb"
longest = ""
current = ""

for char in s:
    if char in current:
        current = current[current.index(char)+1:]
    current += char
    if len(current) > len(longest):
        longest = current

print("Longest substring without repeating characters:", longest)
print("Length:", len(longest))

Explanation:
This uses a sliding window-like approach to track the longest sequence of unique characters.

Output:

Longest substring without repeating characters: abc
Length: 3

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✅ 9. Implement the strstr() Function

def strstr(haystack, needle):
    if needle == "":
        return 0  # As per C/C++ behavior

    for i in range(len(haystack) - len(needle) + 1):
        if haystack[i:i+len(needle)] == needle:
            return i
    return -1

Explanation:
This mimics C’s strstr() function, finding the first occurrence of needle in haystack.

Example:

print(strstr("hello", "lo"))  # Output: 3

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✅ 10. Check if a String Has All Unique Characters

def is_unique(s):
    for char in s:
        if s.count(char) > 1:
            return False
    return True

# Test cases
print(is_unique("abcdef"))  # True
print(is_unique("hello"))   # False

Explanation:
The function checks if any character appears more than once.

Output:

True
False

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🎯 Final Thoughts

These 10 string problems cover:

• Reversal

• Searching

• Replacing

• Frequency analysis

• Palindrome & anagram logic

• Substring and uniqueness detection

They’re excellent for coding practice, interviews, or improving your understanding of string operations in Python.