• Python Features
• Python Installation
• PyCharm Configuration
• Python Variables
• Python Data Types
• Python If Else
• Python Loops
• Python Strings
• Python Lists
• Python Tuples
• Python List Vs Tuple
• Python Sets
• Python Dictionary
• Python Functions
• Python Files I/O
• Read Write Excel
• Read Write JSON
• Read Write CSV
• Python OS Module
• Python Exceptions
• Python Datetime
• Python Collection Module
• Python Sys Module
• Python Decorator
• Python Generators
• Python OOPS
• Python Numpy Module
• Python Pandas Module
• Python Sqlite Module

What is a CSV File?

CSV stands for Comma-Separated Values and is commonly used for tabular data like spreadsheets.

Python has a built-in csv module for handling CSV files.

import csv

---

Write to CSV File

Write Rows Manually

import csv

with open("students.csv", "w", newline="") as file:
    writer = csv.writer(file)
    
    writer.writerow(["Name", "Age", "City"])  # Header
    writer.writerow(["Deepesh", 30, "Delhi"])
    writer.writerow(["Riya", 25, "Mumbai"])

---

Write Multiple Rows (Loop / List)

import csv

data = [
    ["Name", "Age", "City"],
    ["Aman", 28, "Pune"],
    ["Neha", 24, "Chennai"],
    ["Kunal", 29, "Bangalore"]
]

with open("data.csv", "w", newline="") as file:
    writer = csv.writer(file)
    writer.writerows(data)   # write all rows at once

---

Read CSV File

Read and Print Entire File

import csv

with open("students.csv", "r") as file:
    reader = csv.reader(file)
    
    for row in reader:
        print(row)

---

Read CSV as Dictionary

💡 Best when the first row contains headers.

import csv

with open("students.csv", "r") as file:
    reader = csv.DictReader(file)
    
    for row in reader:
        print(row["Name"], row["City"])

---

Write CSV Using Dictionary

import csv

data = [
    {"Name": "Raj", "Age": 27, "City": "Delhi"},
    {"Name": "Simran", "Age": 23, "City": "Kolkata"}
]

with open("students_dict.csv", "w", newline="") as file:
    fieldnames = ["Name", "Age", "City"]
    writer = csv.DictWriter(file, fieldnames=fieldnames)

    writer.writeheader()
    writer.writerows(data)

---

Append to a CSV File

import csv

with open("students.csv", "a", newline="") as file:
    writer = csv.writer(file)
    writer.writerow(["Kiran", 22, "Hyderabad"])

---

Handling Custom Delimiters

Example: Semi-colon ; separated file

import csv

with open("data_semicolon.csv", "r") as file:
    reader = csv.reader(file, delimiter=";")
    for row in reader:
        print(row)

---

Real Example: CSV Filtering

Print only rows where Age > 25

import csv

with open("students.csv", "r") as file:
    reader = csv.DictReader(file)
    
    for row in reader:
        if int(row["Age"]) > 25:
            print(row)

---

Summary

Task	Method
Write row	writer.writerow()
Write multiple rows	writer.writerows()
Read CSV	csv.reader()
Read as dict	csv.DictReader()
Write dict	csv.DictWriter()
Append data	"a" mode
Change delimiter	delimiter=";"