CSV file in Python notes Class 12

CSV File in Python

• CSV stands for Comma Separated Values.
• It is used to store tabular data (rows and columns).
• Data values are separated by commas (,).
• CSV files usually have .csv extension.
• Commonly used in Excel, databases, and data exchange.

Example of CSV file-

RollNo,Name,Marks
101,Aman,85
102,Riya,90
103,Rahul,78

CSV Module in Python

• Python provides a built-in csv module.
• Used to read and write CSV files.

Import CSV Module:

import csv

 Reading CSV File

(a) Using csv.reader()

• Reads data row by row.
• Returns data as a list.

Syntax-

csv.reader(file_object)

Example-

import csv

f=open("student.csv","r")

data=csv.reader(f)

for row in data:
    print(row)

f.close()

Writing CSV File

Using csv.writer()

• Used to write data into CSV file.

Syntax-

csv.writer(file_object)

Example-

import csv

f=open("student.csv","w",newline='')

w=csv.writer(f)

w.writerow(["RollNo","Name","Marks"])
w.writerow([101,"Aman",85])

f.close()

 writerow() Method

• Writes one row at a time.

Syntax-

w.writerow(["Name","City"])

Example-

writerows() Method

• Writes multiple rows together.

rows=[
["Aman","Delhi"],
["Riya","Mumbai"]
]

w.writerows(rows)

Reading CSV using DictReader()

• Reads data as a dictionary.
• First row becomes field names (keys).

import csv

f=open("student.csv","r")

d=csv.DictReader(f)

for row in d:
    print(row)

f.close()

Writing CSV using DictWriter()

• Writes dictionary data into CSV file.

import csv

f=open("student.csv","w",newline='')

fields=["Name","Marks"]

w=csv.DictWriter(f,fieldnames=fields)

w.writeheader()

w.writerow({"Name":"Aman","Marks":85})

f.close()

Important Functions / Methods

Advantages of CSV File

• Easy to create and use.
• Human readable format.
• Supported by Excel and databases.
• Fast data storage and transfer

Disadvantages of CSV File

• No data security.
• Cannot store complex data.
• No formatting support.

Program 1: Write Data into CSV File

import csv

f=open("emp.csv","w",newline='')

w=csv.writer(f)

w.writerow(["EmpID","Name","Salary"])
w.writerow([101,"Aman",25000])

f.close()

Program 2: Read Data from CSV File.

import csv

f=open("emp.csv","r")

r=csv.reader(f)

for i in r:
    print(i)

f.close()

Program 3: Write Multiple Records.

import csv

f=open("student.csv","w",newline='')

w=csv.writer(f)

data=[
["Roll","Name","Marks"],
[1,"Aman",80],
[2,"Riya",90]
]

w.writerows(data)

f.close()

Program 4: Search Record in CSV File.

import csv

f=open("student.csv","r")

r=csv.reader(f)

name=input("Enter name: ")

for i in r:
    if name in i:
        print(i)

f.close()