Python Code to Read and Write a CSV File

A CSV (comma separated values) file stores table data as plain text, one row per line. It can be opened in Excel, and Python has a built-in csv module to work with it.

Read a CSV file

Suppose we have a file named students.csv with this content:

name,marks
Robin,85
Maria,92
John,78

DictReader reads every row as a dictionary, using the first line as the keys.

import csv

total = 0
count = 0

with open("students.csv", newline="") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(row["name"], row["marks"])
        total += int(row["marks"])
        count += 1

print("Average:", total / count)

Output:

Values from a CSV file are always strings, so we used int() for the marks.

Write a CSV file

import csv

rows = [
    ["name", "marks"],
    ["Robin", 85],
    ["Maria", 92],
]

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

print("File saved")

Output:

The new file result.csv will have this content:

name,marks
Robin,85
Maria,92

Related: Python File Handling.

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