Python me File Handling kya hai?

File Handling ka matlab hai computer ki files ke saath kaam karna — files ko padhna (read), likhna (write), kuch aur add karna (append) aur band karna (close). Real applications me data hamesha files me save hota hai — jaise notes app, login systems, log files etc.

Is page me yeh sab sikhenge :-

1. File open karna — open() aur modes
2. File me likhna — write() aur writelines()
3. File padhna — read(), readline(), readlines()
4. File me add karna — append mode
5. with statement — best practice
6. File exist check karna — os module
7. CSV file handling

Note :- Yeh page ek interactive simulator hai. Real Python me files disk pe save hoti hain, lekin yahan hum ek virtual file system use karte hain taaki aap browser me hi sab kuch try kar sakein aur output dekh sakein.

1. File Open Karna — open() aur Modes

Python me file kholne ke liye open() function use hota hai. Isme file ka naam aur mode dena padta hai.

Mode	Matlab	File nahi toh?
"r"	Read — file padhna (default)	FileNotFoundError
"w"	Write — likhna (purana data mit jaata hai)	Nai file ban jaati hai
"a"	Append — end me add karna	Nai file ban jaati hai
"x"	Create — nai file banana	FileExistsError agar already hai
"r+"	Read + Write dono	FileNotFoundError

Example 1: open() modes ka demonstration

Python

In [1]:

print("File Modes:")
print("'r'  — Read mode    : file padhne ke liye")
print("'w'  — Write mode   : likhne ke liye (purana data delete)")
print("'a'  — Append mode  : end me add karna")
print("'x'  — Create mode  : nai file banana")
print("'r+' — Read+Write   : dono kaam")
print()
print("Syntax: f = open('filename.txt', 'mode')")
print("File band karna: f.close()")

Output

2. File Me Likhna — write() aur writelines()

"w" mode me file open karo aur write() se likhو. Agar file pehle se hai toh purana data delete ho jaata hai. writelines() se list ki saari lines ek saath likh sakte hain.

Example 1: File create karke likhna — write()

Python

In [1]:

f = open("notes.txt", "w")   # write mode
f.write("Python bahut aasaan hai.\n")
f.write("Main Python seekh raha hoon.\n")
f.write("File Handling bahut useful hai.\n")
f.close()

print("File 'notes.txt' successfully likhi gayi!")

Output

Example 2: writelines() — list ki saari lines ek saath likhna

Python

In [1]:

students = [
    "Rahul - 88\n",
    "Priya - 95\n",
    "Arjun - 76\n",
    "Neha  - 91\n"
]

f = open("marks.txt", "w")
f.writelines(students)    # list ki saari lines ek baar me
f.close()

print("File 'marks.txt' mein", len(students), "students ke marks likhe gaye!")

Output

3. File Padhna — read(), readline(), readlines()

File padhne ke 3 tarike hain — poori file ek saath, ek line, ya saari lines ki list.

Method	Kaam	Return Type
read()	Poori file ek string me	str
readline()	Ek line padho	str
readlines()	Saari lines ki list	list

Example 1: read() — poori file ek saath padhna

Python

In [1]:

# Pehle file likhte hain
f = open("story.txt", "w")
f.write("Ek baar ki baat hai.\n")
f.write("Ek chhota sa gaon tha.\n")
f.write("Wahan ek Python developer rehta tha.\n")
f.close()

# Ab read karte hain
f = open("story.txt", "r")
content = f.read()     # poori file
f.close()

print("--- File Content ---")
print(content)

Output

Example 2: readline() — ek ek line padhna

Python

In [1]:

# File likhna
f = open("data.txt", "w")
f.write("Line 1: Pehli line\nLine 2: Doosri line\nLine 3: Teesri line\n")
f.close()

# readline() se ek ek line padhna
f = open("data.txt", "r")
line1 = f.readline()    # pehli line
line2 = f.readline()    # doosri line
line3 = f.readline()    # teesri line
f.close()

print(repr(line1))   # \n dikhega
print(repr(line2))
print(repr(line3))

Output

Example 3: readlines() — saari lines list me + loop se padhna

Python

In [1]:

# File likhna
f = open("fruits.txt", "w")
f.write("Apple\nMango\nBanana\nGrapes\nKiwi\n")
f.close()

# readlines() — list milti hai
f = open("fruits.txt", "r")
lines = f.readlines()
f.close()

print("All lines:", lines)
print()
print("Loop se padhna:")
for i, line in enumerate(lines, 1):
    print(f"  Line {i}: {line.strip()}")   # strip() \n hatata hai

Output

4. File Me Add Karna — Append Mode ("a")

Append mode me file ka purana data safe rehta hai aur naya data end me add hota hai. Yeh log files aur diaries ke liye perfect hai.

Example 1: Append — diary me roz nayi entry add karna

Python

In [1]:

# Pehli baar file banana
f = open("diary.txt", "w")
f.write("Day 1: Python install kiya.\n")
f.close()

# Append — nai entries add karo, purani delete nahi hogi
f = open("diary.txt", "a")
f.write("Day 2: Variables aur Data Types seekhe.\n")
f.close()

f = open("diary.txt", "a")
f.write("Day 3: Functions aur OOP padha.\n")
f.close()

# Final file padhna
f = open("diary.txt", "r")
print("--- Diary ---")
print(f.read())
f.close()

Output

Example 2: Write vs Append — fark dekhna

Python

In [1]:

# Write mode — purana data delete ho jaata hai
f = open("test.txt", "w")
f.write("Pehli baar likha.\n")
f.close()

f = open("test.txt", "w")    # dobara write mode
f.write("Doosri baar likha.\n")   # pehla data CHALA GAYA!
f.close()

f = open("test.txt", "r")
print("Write mode ke baad:")
print(f.read())
f.close()

# Append mode — purana data safe rehta hai
f = open("test2.txt", "w")
f.write("Pehli baar likha.\n")
f.close()

f = open("test2.txt", "a")   # append mode
f.write("Doosri baar add kiya.\n")
f.close()

f = open("test2.txt", "r")
print("Append mode ke baad:")
print(f.read())
f.close()

Output

5. with Statement — Best Practice

with statement se file automatically band ho jaati hai — chahe koi error aaye ya nahi. Yeh f.close() likhne se better aur safer hai. Professional code me hamesha with use karna chahiye.

Syntax
with open("filename.txt", "mode") as f: # yahan kaam karo # block khatam hone par file auto-close ho jaati hai

Example 1: with statement se file likhna aur padhna

Python

In [1]:

# with se likhna — f.close() ki zarurat nahi!
with open("student.txt", "w") as f:
    f.write("Name: Rahul\n")
    f.write("Age: 21\n")
    f.write("City: Delhi\n")
    f.write("Marks: 88\n")
# yahan file automatically band ho gayi

# with se padhna
with open("student.txt", "r") as f:
    content = f.read()

print("--- student.txt ---")
print(content)

Output

Example 2: with + loop — multiple students ka data save karna

Python

In [1]:

students = [
    ("Rahul", 88), ("Priya", 95), ("Arjun", 76),
    ("Neha", 91),  ("Vikram", 83)
]

# Write
with open("results.txt", "w") as f:
    f.write("=== Exam Results ===\n")
    for name, marks in students:
        grade = "A" if marks >= 90 else "B" if marks >= 80 else "C"
        f.write(f"{name:<10} {marks}  Grade: {grade}\n")

# Read back
with open("results.txt", "r") as f:
    for line in f:
        print(line.strip())

Output

6. File Exist Check Karna — os Module

os module se file exist karti hai ya nahi check kar sakte hain, file rename, delete aur bahut kuch kar sakte hain.

Example 1: os.path.exists() — file exist karti hai ya nahi

Python

In [1]:

import os

# Pehle ek file banana
with open("check_me.txt", "w") as f:
    f.write("Main exist karta hoon!")

# os.path.exists() — file hai ya nahi
if os.path.exists("check_me.txt"):
    print("check_me.txt exist karti hai!")
else:
    print("File nahi mili.")

if os.path.exists("ghost.txt"):
    print("ghost.txt exist karti hai!")
else:
    print("ghost.txt exist nahi karti.")

# os.path.getsize() — file ka size
size = os.path.getsize("check_me.txt")
print(f"check_me.txt ka size: {size} bytes")

Output

Example 2: os.rename() aur os.remove() — file rename aur delete

Python

In [1]:

import os

# File banana
with open("old_name.txt", "w") as f:
    f.write("Mera naam badla jayega!")

print("old_name.txt exist:", os.path.exists("old_name.txt"))

# Rename karna
os.rename("old_name.txt", "new_name.txt")
print("Rename ke baad:")
print("old_name.txt exist:", os.path.exists("old_name.txt"))
print("new_name.txt exist:", os.path.exists("new_name.txt"))

# Delete karna
os.remove("new_name.txt")
print("Delete ke baad:")
print("new_name.txt exist:", os.path.exists("new_name.txt"))

Output

7. CSV File Handling

CSV (Comma Separated Values) ek popular format hai data store karne ke liye — jaise Excel files. Python ka csv module isse bahut aasaan banata hai.

Example 1: CSV file likhna — csv.writer

Python

In [1]:

import csv

students = [
    ["Name",   "Age", "City",    "Marks"],
    ["Rahul",   21,   "Delhi",    88],
    ["Priya",   20,   "Mumbai",   95],
    ["Arjun",   22,   "Pune",     76],
    ["Neha",    21,   "Chennai",  91]
]

with open("students.csv", "w", newline="") as f:
    writer = csv.writer(f)
    writer.writerows(students)

print("students.csv successfully likhi gayi!")
print("Rows written:", len(students))

Output

Example 2: CSV file padhna — csv.reader aur DictReader

Python

In [1]:

import csv

# Pehle CSV write karte hain
data = [
    ["Product", "Price", "Stock"],
    ["Laptop",  55000,   10],
    ["Phone",   18000,   25],
    ["Tablet",  25000,   15]
]
with open("products.csv", "w", newline="") as f:
    csv.writer(f).writerows(data)

# DictReader se padhna — keys automatically header se milti hain
print("--- Products (DictReader) ---")
with open("products.csv", "r") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(f"{row['Product']:<10} Rs.{row['Price']:<8} Stock: {row['Stock']}")

Output

Quick Summary — File Handling ek nazar me

Concept	Kaam	Example
open("f","r")	File read ke liye kholna	f = open("a.txt","r")
open("f","w")	File write ke liye (reset)	f = open("a.txt","w")
open("f","a")	File append ke liye	f = open("a.txt","a")
write()	String likhna	f.write("hello\n")
writelines()	List likhna	f.writelines(lst)
read()	Poori file padhna	f.read()
readline()	Ek line padhna	f.readline()
readlines()	Saari lines list me	f.readlines()
close()	File band karna	f.close()
with open()	Auto-close (best practice)	with open(...) as f:
os.path.exists()	File exist check	os.path.exists("f.txt")
os.rename()	File rename karna	os.rename("a","b")
os.remove()	File delete karna	os.remove("f.txt")
csv.writer	CSV likhna	csv.writer(f).writerow()
csv.DictReader	CSV dict se padhna	csv.DictReader(f)

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