Read a file line by line in Python

11월 06, 2024

In Python, you can read a file line by line using a for loop, the readline() method, or the readlines() method. Here are three common ways to do it:

1. Using a `for` Loop (Recommended)

This is the most efficient way to read a file line by line because it doesn't load the entire file into memory at once.

# Open the file in read mode
with open("your_file.txt", "r") as file:
    for line in file:
        # Process each line
        print(line.strip())  # .strip() removes trailing newline characters

2. Using `readline()` Method

The readline() method reads one line at a time. You can use it with a while loop to keep reading until the end of the file.

with open("your_file.txt", "r") as file:
    line = file.readline()
    while line:
        print(line.strip())
        line = file.readline()  # Read the next line

3. Using `readlines()` Method

The readlines() method reads all lines in the file and returns them as a list. This can be memory-intensive for large files, so it's best used for smaller files.

with open("your_file.txt", "r") as file:
    lines = file.readlines()
    for line in lines:
        print(line.strip())

Notes

Always use with open(...) as it ensures the file is properly closed after reading.
The strip() method is helpful to remove any trailing newline characters (\n).

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