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How to Read and Write CSV, JSON and Text Files in Python (with open and with)

P9.2 How to Read and Write Text Files in Python

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Why. Logs, notes and simple lists are plain text. Reading them is the first file skill.

What. open(path, mode) opens a file. Modes: "r" read, "w" write (replaces the file), "a" append. The with statement closes the file automatically.

How.

Write then read a text file

  1. Open with with open("file.txt", "w", encoding="utf-8") as f:.
  2. Write with f.write("text\n").
  3. Open again with "r".
  4. Read all with f.read() or line by line with a for loop.
1. with open(...) opens the file2. You read inside the block3. Block ends4. File closes automatically
Reading a file with "with" (read from top to bottom)

Worked example A — Write a small log.

Step 1 — What we do. A support desk in Bengaluru logs three tickets.

Step 2 — Type and run this code.

with open("tickets.txt", "w", encoding="utf-8") as f:
    f.write("T1 login issue\n")
    f.write("T2 refund request\n")
    f.write("T3 address change\n")
print("Saved")

Step 3 — Output you should see.

Saved

Step 4 — What it means. The file is created (or replaced). \n starts a new line.

Worked example B — Read it back line by line.

Step 1 — What we do. We read the same log and count lines.

Step 2 — Type and run this code.

with open("tickets.txt", "w", encoding="utf-8") as f:
    f.write("T1 login issue\nT2 refund request\nT3 address change\n")
count = 0
with open("tickets.txt", encoding="utf-8") as f:
    for line in f:
        count += 1
        print(line.strip())
print("Lines:", count)

Step 3 — Output you should see.

T1 login issue
T2 refund request
T3 address change
Lines: 3

Step 4 — What it means. Each line includes \n at the end, so .strip() removes it.

Worked example C — Append a new line.

Step 1 — What we do. A new ticket arrives. "a" adds to the end instead of replacing.

Step 2 — Type and run this code.

with open("tickets.txt", "w", encoding="utf-8") as f:
    f.write("T1 login issue\n")
with open("tickets.txt", "a", encoding="utf-8") as f:
    f.write("T4 card blocked\n")
print(open("tickets.txt", encoding="utf-8").read())

Step 3 — Output you should see.

T1 login issue
T4 card blocked

Step 4 — What it means. "w" would have wiped T1. Use "a" to keep old lines.

Ravindra Bagale's Tip

Always pass encoding="utf-8". It keeps ₹, €, £ and Marathi/Hindi text safe on every computer.