Python Basics 9

File I/O in Python, Opening a File in Python, Writing a File in Python...

Index

1. File I/O in Python

2. Types of Files in Python

3. Opening, Reading, and Closing a File in Python

4. Writing a File in Python

5. Deleting a File in Python

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1. File I/O in Python

Definition:
File Input/Output (I/O) in Python refers to the process of reading data from files and writing data to files. Python provides built-in functions and methods to handle file operations efficiently.

Use-Case Example:
File I/O is essential when you need to save data generated by a program, log outputs, or read input data from a file for processing.

Syntax:

# Opening a file
file = open("filename", "mode")

# Reading from a file
content = file.read()

# Writing to a file
file.write("data")

# Closing a file
file.close()

Rules:

• Always close files after performing I/O operations to free system resources.

• Handle exceptions to manage errors during file operations, such as file not found or permission denied.

• Use different modes (r, w, a, etc.) based on the operation (reading, writing, appending).

Basic Example:

# Opening and reading a file
file = open("example.txt", "r")
content = file.read()
print(content)  # Output: Content of example.txt
file.close()

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2. Types of Files in Python

Definition:
Files in Python can be broadly categorized into two types: text files and binary files. Text files contain human-readable characters, while binary files contain data in a format not intended for human reading.

Use-Case Example:
Text files are used to store simple data like logs, configuration files, or CSV data. Binary files are used to store images, videos, and executable files.

Syntax:

# Example of opening different types of files
text_file = open("document.txt", "r")
binary_file = open("image.png", "rb")

Rules:

• Text files are typically opened with modes like r, w, a, while binary files use rb, wb, ab.

• The content of binary files should be handled as bytes.

Basic Example:

# Reading a text file
text_file = open("example.txt", "r")
print(text_file.read())  # Output: Content of example.txt
text_file.close()

# Reading a binary file (example for context, not practical to print binary content)
binary_file = open("example.bin", "rb")
binary_content = binary_file.read()
print(binary_content)  # Output: b'\x89PNG\r\n\x1a\n...'
binary_file.close()

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3. Opening, Reading, and Closing a File in Python

Definition:
Opening a file in Python is the first step before performing any operation (reading or writing). After opening a file, you can read its content or write data to it. Once the operations are done, the file should be closed to free up system resources.

Use-Case Example:
Reading configuration data from a file to initialize program settings.

Syntax:

# Opening a file
file = open("filename", "mode")

# Reading from a file
content = file.read()

# Closing a file
file.close()

Rules:

• Files must be opened in the correct mode based on the operation (r for reading, w for writing, a for appending).

• Always close files after operations to avoid resource leaks.

Basic Example:

# Opening and reading a file
file = open("example.txt", "r")
content = file.read()
print(content)  # Output: Content of example.txt
file.close()

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4. Writing a File in Python

Definition:
Writing to a file in Python involves opening the file in write (w) or append (a) mode and then writing data to it. If the file doesn’t exist, it is created.

Use-Case Example:
Saving user-generated data, such as form inputs or program outputs, to a text file.

Syntax:

# Opening a file in write mode
file = open("filename", "w")

# Writing to the file
file.write("data")

# Closing the file
file.close()

Rules:

• Opening a file in w mode will overwrite the existing content. Use a mode to append data.

• Ensure the file is properly closed after writing to save changes.

Basic Example:

# Writing to a file
file = open("output.txt", "w")
file.write("This is a sample text.")
file.close()

# Check the file content
file = open("output.txt", "r")
print(file.read())  # Output: This is a sample text.
file.close()

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5. Deleting a File in Python

Definition:
Deleting a file in Python can be done using the os module, which provides functions to interact with the operating system, including file deletion.

Use-Case Example:
Deleting temporary files or cleaning up after processing data files.

Syntax:

import os

# Deleting a file
os.remove("filename")

Rules:

• Ensure the file exists before attempting to delete it to avoid errors.

• Handle exceptions to manage situations where the file cannot be deleted (e.g., permission issues).

Basic Example:

import os

# Deleting a file
if os.path.exists("output.txt"):
    os.remove("output.txt")
    print("File deleted.")
else:
    print("File does not exist.")

# Output: File deleted. (if the file existed)

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Python Basics by - Vishal Rajput