Writing Files in Python

Learn how to create files, write data, append new content and save information using Python.

What is Writing to a File?

Writing to a file means storing data inside a file using a Python program.

Python provides different file modes such as w, a and x for writing and creating files.

Why Do We Write Data to Files?

Writing Files Diagram

The basic process of writing data to a file is:

1. Write Mode - w

The w mode is used to write data into a file.

If the file does not exist, Python creates it.

If the file already contains data, writing with w can replace the existing content.

file = open("example.txt", "w")

file.write("Hello Python")

file.close()

After running the program, the file can contain:

Hello Python

Writing with the with Statement

A common and convenient approach is to use with.

with open("example.txt", "w") as file:

    file.write("Hello Python")

    file.write("\nWelcome to CIIT")

After the block finishes, Python handles the file resource automatically.

Writing Multiple Lines

We can use newline characters such as \n to write multiple lines.

with open("students.txt", "w") as file:

    file.write("Rahul\n")
    file.write("Priya\n")
    file.write("Amit\n")
    file.write("Sneha\n")

The file content becomes:

Rahul
Priya
Amit
Sneha

2. Append Mode - a

The a mode is used to add new content at the end of an existing file.

Existing content remains unchanged.

with open("students.txt", "a") as file:

    file.write("Neha\n")

If the file already contains:

Rahul
Priya
Amit
Sneha

After appending, it can contain:

Rahul
Priya
Amit
Sneha
Neha

Write vs Append

3. Create Mode - x

The x mode is used to create a new file.

If a file with the same name already exists, Python raises an error instead of replacing it.

file = open("newfile.txt", "x")

file.write("New file created")

file.close()

This mode is useful when you want to create a file only if it does not already exist.

Writing Multiple Lines with writelines()

The writelines() method can write a sequence of strings to a file.

students = [
    "Rahul\n",
    "Priya\n",
    "Amit\n"
]

with open("students.txt", "w") as file:

    file.writelines(students)

The strings are written in the same order.

Writing List Data to a File

We can take data from a Python list and write each item into the file.

students = [
    "Rahul",
    "Priya",
    "Amit"
]

with open("students.txt", "w") as file:

    for student in students:

        file.write(student + "\n")

The list data is stored one item per line.

Writing User Input to a File

We can get data from the user and store it in a file.

name = input("Enter your name: ")

with open("user.txt", "w") as file:

    file.write(name)

print("Data saved successfully")

The entered name is stored inside user.txt.

Append User Input

We can keep adding user entries without deleting previous data.

name = input("Enter your name: ")

with open("students.txt", "a") as file:

    file.write(name + "\n")

print("Student added")

Every new name is added at the end of the file.

Writing with Encoding

We can specify an encoding while opening a file.

with open(
    "message.txt",
    "w",
    encoding="utf-8"
) as file:

    file.write("Hello Python")
    file.write("\nWelcome to Python")

UTF-8 is commonly used when working with Unicode text.

Using New Line Characters

The \n character is used to move to the next line.

with open("example.txt", "w") as file:

    file.write("Line 1\n")
    file.write("Line 2\n")
    file.write("Line 3\n")

File content:

Line 1
Line 2
Line 3

Example: Student Data 👨‍🏫📩

Let's store student information in a text file.

students = [
    "Rahul - Python",
    "Priya - Java",
    "Amit - .NET",
    "Sneha - MERN"
]

with open("students.txt", "w") as file:

    for student in students:

        file.write(student + "\n")

print("Student data saved")

The file can contain:

Rahul - Python
Priya - Java
Amit - .NET
Sneha - MERN

Handling File Writing Errors

File operations can sometimes fail because of permission issues, invalid paths or other problems.

We can use try and except to handle errors.

try:

    with open("example.txt", "w") as file:

        file.write("Hello Python")

except OSError:

    print("Unable to write to the file")

Important Writing Modes

Best Practices

Common Mistakes

• Using w mode when existing content should be preserved.
• Forgetting newline characters when writing multiple lines.
• Using an incorrect file path.
• Not handling possible file errors.
• Writing text using an inappropriate encoding.

Practice Programs

1. Create a file named students.txt using w mode.
2. Write five student names into the file.
3. Add another student using a mode.
4. Create a file using x mode.
5. Write a list of courses into a file.
6. Get a student's name using input() and save it to a file.
7. Create a simple student report in a text file.