Mastering File Handling in Python: A Complete Guide

File handling is an essential skill in Python, as it allows you to read, write, update, and delete files. In this blog, we’ll explore various file operations and modes, handling text and binary files, managing file pointers, handling exceptions, and even working with temporary files. Let's dive in!

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File Modes Overview

Python’s open() function lets you specify modes:

• 'r': Read-only mode

• 'w': Write mode (overwrites if file exists)

• 'a': Append mode

• 'b': Binary mode

• 't': Text mode (default)

• 'x': Create mode (fails if file exists)

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Basic Operations

Opening and Reading a File

The open() function opens a file, and the read() function reads its content. It’s a best practice to close files after use.

file = open("example.txt", "r")
print(file.read())
file.close()

Output (example):

Hello, this is the content of example.txt.

Using with to Open Files

Using with automatically closes the file.

with open("example.txt", "r") as file:
    content = file.read()
    print(content)

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Writing to a File

Write Mode

This overwrites the file if it exists or creates a new one.

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

Reading it back:

with open("example.txt", "r") as file:
    content = file.read()
    print(content)

Output:

Hello World

Appending to a File

with open("output.txt", "a") as file:
    file.write("Fourth Line\n")

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Reading Specific Parts of a File

Reading a Certain Number of Characters

with open("output.txt", "r") as file:
    content = file.read(10)
    print(content)

Output:

First line

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Using tell() and seek()

• tell() returns the current pointer position.

• seek() sets the pointer to a specific location.

with open("output.txt", "r") as file:
    print(file.read(10))  # Reads first 10 characters
    print(file.tell())    # Shows the position (10)
    file.seek(0)          # Resets pointer to beginning
    print(file.read(10))  # Reads first 10 characters again

Output:

First line
10
First line

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Binary File Handling

Binary files, like images, are read and written in binary mode.

with open("image.jpg", "rb") as source_file:
    with open("copy.jpg", "wb") as dest_file:
        dest_file.write(source_file.read())

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Exception Handling

Handle exceptions to prevent crashes when files don't exist or can’t be accessed.

try:
    with open("notexist.txt", "r") as file:
        content = file.read()
except FileNotFoundError:
    print("The file doesn't exist.")

Output:

The file doesn't exist.

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Using the os and shutil Libraries

These libraries let you manage files, like deleting or moving them.

import os
import shutil

try:
    os.remove("copy.jpg")
except FileNotFoundError:
    print("The file is not present.")

# Moving a file
shutil.move("image.jpg", "Files/image.jpg")

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Temporary Files

The tempfile module allows creating temporary files that are deleted once closed.

import tempfile

with tempfile.TemporaryFile(mode="w+t") as temp_file:
    temp_file.write("Temporary content\n")
    temp_file.seek(0)
    print(temp_file.read())

Output:

Temporary content

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Conclusion

With Python's extensive file handling capabilities, you can efficiently manage data across different file formats and sizes. Whether working with text or binary files, handling errors, or creating temporary files, file handling is a powerful tool in Python’s toolkit.