How to read a file line-by-line into a list?

Reading a file line-by-line into a list in Python is a common task, especially when dealing with text data like logs, CSVs, or configuration files. Python makes this process very straightforward and efficient.

The most Pythonic and memory-efficient way is using a context manager with the built-in open() function:

with open('filename.txt', 'r') as file:
    lines = file.readlines()

Key points:

• with statement: Ensures the file is automatically closed after you're done reading it, which is a good practice.
  
• readlines(): Reads the entire file line by line and stores each line as an element in a list.
  

If you want to avoid newline characters (
), you can use a list comprehension:

with open('filename.txt', 'r') as file:
    lines = [line.strip() for line in file]

Other things to keep in mind:

If the file is very large, readlines() might use too much memory. In such cases, iterate over the file directly:

lines = []
with open('filename.txt', 'r') as file:
    for line in file:
        lines.append(line.strip())

• Always handle potential exceptions using try-except blocks, especially for file operations.