1. Learning Objectives
2. Prerequisites
3. Introduction
4. What are File Modes?
5. Why are File Modes Required?
6. Types of File Modes
7. Text Modes
8. Binary Modes
9. File Pointer Behavior
10. File Mode Comparison
11. Internal Working
12. Summary

After completing this chapter, you will be able to:

• Understand file modes.
• Differentiate read, write, append, and create modes.
• Work with update modes.
• Understand binary file modes.
• Learn file pointer behavior.
• Select the correct mode for different scenarios.

Before learning this chapter, you should know:

• File Handling Basics
• open() Function
• Reading and Writing Files

When opening a file,

Python needs to know how the file will be used.

For example,

• Read existing data
• Write new data
• Append data
• Create a new file
• Read and write together

This is specified using File Modes.

A File Mode specifies the purpose for which a file is opened.

It tells Python what operations are allowed on the file.

File modes tell Python how to open and use a file.

Different operations require different permissions.

For example:

• Reading requires read permission.
• Writing requires write permission.
• Appending requires append permission.

Using the wrong mode can lead to errors or accidental data loss.

Used for reading an existing file.

If the file does not exist,

Python raises

FileNotFoundError

Example

file = open("student.txt", "r")

Used for writing data.

If the file exists,

its previous contents are removed.

If it does not exist,

Python creates a new file.

Example

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

Adds new data to the end of the file.

Existing data remains unchanged.

Example

file = open("student.txt", "a")

Creates a new file.

If the file already exists,

Python raises

FileExistsError

Example

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

Allows both reading and writing.

The file must already exist.

Example

file = open("student.txt", "r+")

Allows reading and writing.

Existing content is erased before writing.

Example

file = open("student.txt", "w+")

Allows appending and reading.

Existing content is preserved.

Example

file = open("student.txt", "a+")

Binary files contain non-text data.

Examples

• Images
• Videos
• Audio
• PDF Documents
• Executables

Binary modes include:

rb

wb

ab

Example

file = open("photo.jpg", "rb")

Whenever a file is opened,

Python maintains a file pointer.

The file pointer indicates the current reading or writing position.

Example

Python

↓

File Opened

↓

Pointer at Beginning

↓

Read()

↓

Pointer Moves Forward

Program Starts

↓

open(file, mode)

↓

Operating System Checks Mode

↓

Permission Granted

↓

File Object Created

↓

Operation Performed

↓

close()

↓

Program Ends

• Controls file access.
• Prevents accidental operations.
• Supports different use cases.
• Works with text and binary files.
• Improves application safety.

• Use the least permissive mode required.
• Avoid w unless overwriting is intended.
• Use a for logs and reports.
• Use x when creating new files safely.
• Use binary modes for non-text files.

Using w instead of a.

This removes existing content.

Opening a binary file using text mode.

Using r when the file does not exist.

Raises

FileNotFoundError

Using x when the file already exists.

Raises

FileExistsError

file = open("student.txt", "r")

print(file.read())

file.close()

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

file.write("Python")

file.close()

file = open("student.txt", "a")

file.write("\nAdvanced Python")

file.close()

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

file.close()

file = open("student.txt", "r+")

print(file.read())

file.write("\nNew Record")

file.close()

file = open("student.txt", "w+")

file.write("Python")

file.seek(0)

print(file.read())

file.close()

seek(0) moves the file pointer back to the beginning before reading.

file = open("student.txt", "a+")

file.write("\nNew Line")

file.seek(0)

print(file.read())

file.close()

file = open("photo.jpg", "rb")

data = file.read()

print(type(data))

file.close()

<class 'bytes'>

file = open("sample.bin", "wb")

file.write(b"Python")

file.close()

file = open("sample.bin", "ab")

file.write(b"123")

file.close()

Program Starts

↓

Choose File Mode

↓

Open File

↓

File Pointer Created

↓

Perform Operation

↓

Close File

↓

Program Ends

Python Program

│

├── File Object

│      │

│      ├── Mode : r

│      ├── Pointer

│      └── Data

│

└── student.txt

A file mode specifies how a file is opened and what operations are permitted.

r

The file is opened for writing.

If it exists, its contents are overwritten.

If it does not exist, a new file is created.

• w overwrites existing data.
• a preserves existing data and appends new data.

x

It allows both reading and writing without automatically overwriting the file.

It moves the file pointer to the beginning of the file.

• rb
• wb
• ab

FileExistsError

FileNotFoundError

1. Open a file using every file mode.
2. Compare w and a.
3. Read and write using r+.
4. Use seek() after writing.
5. Read a binary file.

• r → Read
• w → Write (Overwrite)
• a → Append
• x → Create New File
• r+ → Read + Write
• w+ → Write + Read
• a+ → Append + Read
• rb → Read Binary
• wb → Write Binary
• ab → Append Binary

In this chapter, we learned:

• File Modes
• Text Modes
• Binary Modes
• File Pointer
• File Mode Comparison
• Practical Programs
• Advantages
• Best Practices
• Common Mistakes
• Interview Questions
• Practice Programs
• Quick Revision