🟢 Beginner · Lesson 15

String Handling in Python

Python में String Handling

What is a String?

A string is text — a sequence of characters inside quotes. Strings are immutable (cannot be changed in place); any "change" creates a new string.

Python – str.py

name = "CodeKaFunda"
print(name)
print(len(name))   # number of characters

CodeKaFunda 11

Indexing & Slicing

Each character has an index starting at 0. Negative indexes count from the end.

Python – slice.py

word = "PYTHON"
print(word[0])      # first
print(word[-1])     # last
print(word[0:3])    # characters 0,1,2
print(word[::-1])   # reversed

P N PYT NOHTYP

word[0] = first char; word[-1] = last char.
word[0:3] = slice from 0 up to (not including) 3.
[::-1] reverses the whole string.

Useful String Methods

Method	Does	Example
.upper()	UPPERCASE	"hi".upper() → HI
.lower()	lowercase	"HI".lower() → hi
.strip()	remove spaces	" hi ".strip() → hi
.replace()	swap text	"cat".replace("c","b") → bat
.split()	break into list	"a b".split() → [a, b]
.find()	position of text	"abc".find("b") → 1

Program 1: Length & Case

Python – case.py

text = input("Enter text: ")
print("Length    :", len(text))
print("Uppercase :", text.upper())
print("Lowercase :", text.lower())
print("Title     :", text.title())

Enter text: hello world Length : 11 Uppercase : HELLO WORLD Lowercase : hello world Title : Hello World

Program 2: Reverse & Palindrome Check

Python – palindrome.py

word = input("Enter a word: ").lower()
reversed_word = word[::-1]

if word == reversed_word:
    print(word, "is a Palindrome")
else:
    print(word, "is NOT a Palindrome")

Enter a word: Madam madam is a Palindrome

.lower() makes the check case-insensitive.
word[::-1] reverses it; if it equals the original, it is a palindrome.

Program 3: Count Vowels

Python – vowels.py

text = input("Enter text: ").lower()
count = 0
for ch in text:
    if ch in "aeiou":
        count += 1
print("Vowels:", count)

Enter text: Education Vowels: 5

The loop checks each character; ch in "aeiou" is True only for vowels.

Program 4: Word Count

Python – wordcount.py

sentence = input("Enter a sentence: ")
words = sentence.split()
print("Total words:", len(words))
print("Words:", words)

Enter a sentence: I love Python programming Total words: 4 Words: ['I', 'love', 'Python', 'programming']

.split() breaks the sentence at spaces into a list; len() counts the items.

Common Mistakes

Trying to change a character: s[0] = "X" fails (strings are immutable).
Forgetting .lower() before comparing text.
Confusing index (position) with the character itself.

Practice Tasks

Ask for a name and print it in uppercase and reversed.
Count how many times a letter appears in a word.
Check if a sentence is a palindrome (ignore spaces).
Replace all spaces in a string with underscores.

Summary

Strings are immutable sequences of characters; index starts at 0.
Slicing [start:stop:step] extracts parts; [::-1] reverses.
Common methods: upper, lower, strip, replace, split, find.

String क्या है?

String text है — quotes के अंदर characters का sequence। Strings immutable हैं (जगह पर बदली नहीं जा सकतीं); कोई भी "बदलाव" नई string बनाता है।

Python – str.py

name = "CodeKaFunda"
print(name)
print(len(name))   # characters की संख्या

CodeKaFunda 11

Indexing और Slicing

हर character का index 0 से शुरू होता है। Negative index अंत से गिनता है।

Python – slice.py

word = "PYTHON"
print(word[0])      # पहला
print(word[-1])     # आखिरी
print(word[0:3])    # characters 0,1,2
print(word[::-1])   # उल्टा

P N PYT NOHTYP

word[0] = पहला char; word[-1] = आखिरी char।
word[0:3] = 0 से 3 (शामिल नहीं) तक slice।
[::-1] पूरी string उल्टी कर देता है।

उपयोगी String Methods

Method	क्या करता है	Example
.upper()	UPPERCASE	"hi".upper() → HI
.lower()	lowercase	"HI".lower() → hi
.strip()	spaces हटाना	" hi ".strip() → hi
.replace()	text बदलना	"cat".replace("c","b") → bat
.split()	list में तोड़ना	"a b".split() → [a, b]
.find()	text की position	"abc".find("b") → 1

Program 1: Length और Case

Python – case.py

text = input("Enter text: ")
print("Length    :", len(text))
print("Uppercase :", text.upper())
print("Lowercase :", text.lower())
print("Title     :", text.title())

Enter text: hello world Length : 11 Uppercase : HELLO WORLD Lowercase : hello world Title : Hello World

Program 2: Reverse और Palindrome Check

Python – palindrome.py

word = input("Enter a word: ").lower()
reversed_word = word[::-1]

if word == reversed_word:
    print(word, "is a Palindrome")
else:
    print(word, "is NOT a Palindrome")

Enter a word: Madam madam is a Palindrome

.lower() check को case-insensitive बनाता है।
word[::-1] उल्टा करता है; original के बराबर हो तो palindrome।

Program 3: Vowels गिनें

Python – vowels.py

text = input("Enter text: ").lower()
count = 0
for ch in text:
    if ch in "aeiou":
        count += 1
print("Vowels:", count)

Enter text: Education Vowels: 5

Loop हर character check करता है; ch in "aeiou" सिर्फ vowels के लिए True होता है।

Program 4: Word Count

Python – wordcount.py

sentence = input("Enter a sentence: ")
words = sentence.split()
print("Total words:", len(words))
print("Words:", words)

Enter a sentence: I love Python programming Total words: 4 Words: ['I', 'love', 'Python', 'programming']

.split() sentence को spaces पर list में तोड़ता है; len() items गिनता है।

सामान्य गलतियाँ

character बदलने की कोशिश: s[0] = "X" fail होता है (strings immutable)।
text compare करने से पहले .lower() भूलना।
index (position) को character समझ लेना।

Practice Tasks

नाम पूछकर uppercase और reversed में print करें।
किसी word में कोई letter कितनी बार आता है, गिनें।
Check करें कि sentence palindrome है (spaces ignore करें)।
String के सभी spaces को underscores से replace करें।

सारांश

Strings characters का immutable sequence हैं; index 0 से शुरू।
Slicing [start:stop:step] हिस्से निकालता है; [::-1] उल्टा करता है।
Common methods: upper, lower, strip, replace, split, find।

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