7 3 2 writelines() Explained

Key Concepts

The writelines() method in Python is used to write a list of strings to a file. The key concepts include:

• Writing multiple lines
• Handling file objects
• Appending lines to an existing file
• Practical applications

1. Writing Multiple Lines

The writelines() method takes a list of strings and writes each string as a separate line in the file.

Example:

lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
with open('example.txt', 'w') as file:
    file.writelines(lines)
    

Analogy: Think of writing multiple post-it notes and sticking them on a wall, each note representing a line in the file.

2. Handling File Objects

It's important to open and close files properly to avoid resource leaks. Using the with statement ensures the file is closed automatically.

Example:

with open('example.txt', 'w') as file:
    lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
    file.writelines(lines)
    

Analogy: Think of a library book that automatically returns itself to the shelf when you're done writing.

3. Appending Lines to an Existing File

You can append lines to an existing file by opening it in append mode ('a') and using the writelines() method.

Example:

with open('example.txt', 'a') as file:
    lines = ["Line 4\n", "Line 5\n"]
    file.writelines(lines)
    

Analogy: Think of adding new pages to a book, where the existing content remains intact.

4. Practical Applications

The writelines() method is useful for logging, writing configuration files, and more.

Example:

log_entries = ["User logged in\n", "File uploaded\n", "User logged out\n"]
with open('log.txt', 'a') as log_file:
    log_file.writelines(log_entries)
    

Analogy: Think of writing entries in a diary, where each entry represents a line in the log file.

Putting It All Together

By understanding and using the writelines() method effectively, you can efficiently handle file operations in Python.

Example:

with open('example.txt', 'w') as file:
    lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
    file.writelines(lines)

with open('example.txt', 'a') as file:
    lines = ["Line 4\n", "Line 5\n"]
    file.writelines(lines)