Lesson 3: Input, Output & Working with Strings in Python

Divya October 14, 2025
Input, Output & Working with Strings in Python

Bro, agar tu Python seekh raha hai na, toh aaj ka topic ekdum base strong karne wala hai — Input, Output aur Strings. Ye teen cheezein aisi hain jo har Python project mein kaam aati hain — chaahe tu calculator bana raha ho, game bana raha ho, ya koi web app. Samajh ja, ye topic ignore kar gaya toh future mein “SyntaxError” se dosti karni padegi 😂

Mujhe yaad hai jab maine pehli baar Python likha tha. Console pe likha print("Hello World") aur socha — bas itna hi? Matlab itna simple? Aur tabhi se love story start ho gayi. Python ke saath ❤️

Taking Input from Users — Tumhara pehla interaction with user 😁

Ab bhai maan le tu koi program bana raha hai jo user se naam poochta hai aur use greet karta hai. Simple sa scene hai. Toh Python mein input lene ka tarika hai:

name = input("Enter your name: ")
print("Hello", name)

Yahan pe kya ho raha hai? input() function user se data leta hai (console se). Jo bhi user type karega wo ek string ke form mein return hota hai.

Matlab agar user ne likha Ritik, toh variable name mein ab "Ritik" store ho gaya. Easy? Bilkul.

Lekin ek chhota twist hai bro — chahe user number type kare, input() hamesha string hi deta hai. Toh agar tu likhe:

age = input("Enter your age: ")
print(age + 2)

Toh Python gussa ho jayega 😡 aur bolega — “TypeError: can only concatenate str (not int) to str”

Kyuki age string hai! Toh number banane ke liye tu likh:

age = int(input("Enter your age: "))
print(age + 2)

Ab kaam karega mast. Simple funda — jo bhi numeric input lena ho, usse int() ya float() mein convert kar le.

Formatting Output — Ban jao stylish developer 💅

Bro, print karna toh sab karte hain, par professional developers print karte hain style ke saath! Dekh:

1. Old-school way (comma wala)

name = "Ritik"
age = 22
print("My name is", name, "and I am", age, "years old.")

Thoda outdated hai, but kaam karta hai. Problem ye hai ki space ka control nahi rehta. Har comma ek extra space add karta hai.

2. Using format()

print("My name is {} and I am {} years old.".format(name, age))

Ye thoda cool lagta hai. Tu curly braces mein values inject kar sakta hai. Advanced version bhi hai:

print("My name is {0} and I am {1} years old. {0} loves Python!".format(name, age))

Yahan {0} aur {1} placeholders hain — order se values jayengi.

3. f-Strings — Python ka fashion statement 💫

print(f"My name is {name} and I am {age} years old.")

Bas string ke aage ‘f’ lagao, aur direct variable likh do curly braces ke andar. Ye hai Python 3.6+ ka best feature. Simple, readable aur professional.

Strings in Depth — Yeh topic deep hai bro 😎

Python mein string ek sequence hoti hai characters ka. Matlab har ek letter, ek index pe hota hai. Jaise:

word = "Python"

Toh:

  • word[0] = 'P'
  • word[1] = 'y'
  • word[-1] = 'n' (last character)

Chal ek try karte hain:

word = "Python"
print(word[0])   # Output: P
print(word[-1])  # Output: n

Ab baat karte hain slicing ki. Matlab string ke ek portion ko nikalna.

print(word[0:4])

Output: Pyth

Matlab 0 se start karke 4 ke pehle tak. (4th index included nahi hota). Ye typical Python style hai — end exclusive.

Tu aise bhi likh sakta hai:

print(word[:3])   # start se 3 tak
print(word[2:])   # 2 se end tak
print(word[:])    # full string

Easy aur powerful dono.

Concatenation & Repetition — Jab strings milte hain 💘

String concat karna matlab unhe jodna.

a = "Hello"
b = "Bro"
print(a + " " + b)

Output: Hello Bro

Repetition bhi kar sakte ho bro:

print("Ha" * 3)

Output: HaHaHa

Python har cheez expressive bana deta hai. Bas logic samajh aur code likh.

Common Beginner Mistakes 😅

  • 1. Forgetting to convert input to int/float.
  • 2. Using wrong string index (jaise word[10] when string shorter).
  • 3. Confusing print formatting methods.
  • 4. Trying to modify string directly (bro, strings immutable hote hain!).

Example:

word = "Python"
word[0] = "J"   # ❌ Error!

Strings ko change nahi kar sakte directly. Par naya bana sakte ho:

new_word = "J" + word[1:]
print(new_word)

Output: Jython

See? Smart workaround 😏

String Methods — Bro ye toh Python ke secret hacks hain 🔥

Ab scene aisa hai bhai... Python ke strings ke paas kuch built-in superpowers hote hain — jinhe hum “methods” bolte hain. Matlab tu string pe dot laga ke kuch bhi karwa sakta hai. Jaise:

1. upper() – sab letters ko CAPITAL bana dega.
2. lower() – sab chhote kar dega, bilkul humble mode.
3. title() – har word ka pehla letter royal bana dega.
4. replace() – ek cheez hata ke doosri daal de, jaise naam change karna 😎
5. split() – string tod ke list bana dega.
6. join() – list ko jod ke ek string bana dega.
7. strip() – starting aur ending ke extra spaces uda dega.
8. find() – substring kidhar hai ye batayega.
9. count() – ek word kitni baar aaya, ye ginti karega.

Chal, thoda practice kar le:

msg = "   python is fun   "

print(msg.upper())     # PYTHON IS FUN
print(msg.strip())     # python is fun
print(msg.replace("fun", "awesome"))   # python is awesome

Dekha? Bas ek method lagaya aur pura mood change. Python literally ek magician hai.

Ab ye split aur join combo dekho — ye toh pura jugalbandi hai 😂

words = "I love Python".split()
print(words)   # ['I', 'love', 'Python']

joined = "-".join(words)
print(joined)  # I-love-Python

Split string ko parts mein tod deta hai, aur join unhe jod ke ek stylish version bana deta hai. Simple but cool.

Bas ek cheez yaad rakh bro — ye sab methods original string ko change nahi karte. Python ke strings immutable hote hain. Matlab agar tu kuch modify karega, toh wo actually ek nayi string return karega. Original untouched rahega — jaise ex ko ignore kar dena 😂

Mini Project Time 🧠 — Username Formatter

Ab theory kaafi ho gayi. Thoda haath ganda karte hain. Banaate hain ek chhota sa project jisme user apna naam daale aur hum uske liye ek cool username generate kar dein.

Goal: Simple — user ka naam lo, clean karo, sab lowercase mein lao, spaces hatao aur ek random number chipka do. Chalo code likhte hain 👇

import random

full_name = input("Enter your full name: ")

# Step 1: Remove extra spaces
clean_name = full_name.strip()

# Step 2: Convert to lowercase
lowered = clean_name.lower()

# Step 3: Replace spaces with underscores
username_base = lowered.replace(" ", "_")

# Step 4: Add random number for uniqueness
random_num = random.randint(100, 999)

username = f"{username_base}_{random_num}"

print("Your new username is:", username)

Output kuch aisa aayega:

Enter your full name:  Ritik Kumar  
Your new username is: ritik_kumar_437

Dekha? Simple aur ekdum reusable. Aise username tu kisi game, website, ya login system mein use kar sakta hai. Ekdum real-world wala kaam.

Bonus Tip: Validation bhi zaroori hai 💡

Ab maan le user kuch bhi random likh de — jaise numbers ya special characters. Toh check karne ke liye Python ke paas ready-made methods hain.

name = input("Enter your name: ")

if name.isalpha():
    print("Valid name bro!")
else:
    print("Invalid name — sirf letters likh na yaar.")

Yahan isalpha() check karta hai ki naam sirf alphabets mein hai ya nahi.

Baaki kuch aur useful checks bhi hain:

  • isdigit() – agar string mein sirf numbers hain.
  • isalnum() – letters + numbers (no symbols).
  • startswith() / endswith() – prefix ya suffix check karne ke liye.

Thoda test kar, mix kar, aur maza le. Python yahan bhi super chill hai.

Bro-to-Bro Gyaan 💬

Sun bhai, jitna tu khud likhega na — utna samjhega. YouTube pe dekh ke ya copy-paste se thoda aata hai, par asli fun tab hai jab tu khud galti kare, fir fix kare. Ye hi developer life ka asli vibe hai 😎

Ye input-output aur string concepts chhote lagte hain, par ye foundation strong karte hain. Aage jab tu Flask, Django, ya koi API banayega, tab ye hi kaam aayega.

So agla time jab tu likhe print(f"Hello {name}") — samajh le bhai, tu ek level aur upar chala gaya hai 💪

Next Steps 🚀

  • Ek palindrome checker bana — dekh string ulta likhne pe same hai ya nahi.
  • Ek small validation system bana — jisme user ka naam aur age check ho.
  • Agla blog? Conditional Statements (if, elif, else) — wahaan logic ka real maza hai 🔥

Tab tak ke liye, coding kar, chill kar, aur Python se dosti banaye rakh ❤️

—(Python + Coffee = Code 💻☕)

Divya

Posted by Divya

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