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

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


This code will read the entire file into memory and remove all whitespace characters (newlines and spaces) from the end of each line:

with open(filename) as file:    lines = file.readlines()    lines = [line.rstrip() for line in lines]

If you're working with a large file, then you should instead read and process it line-by-line:

with open(filename) as file:    for line in file:        print(line.rstrip())

In Python 3.8 and up you can use a while loop with the walrus operator like so:

with open(filename) as file:    while (line := file.readline().rstrip()):        print(line)

Depending on what you plan to do with your file and how it was encoded, you may also want to manually set the access mode and character encoding:

with open(filename, 'r', encoding='UTF-8') as file:    while (line := file.readline().rstrip()):        print(line)


See Input and Ouput:

with open('filename') as f:    lines = f.readlines()

or with stripping the newline character:

with open('filename') as f:    lines = [line.rstrip() for line in f]


This is more explicit than necessary, but does what you want.

with open("file.txt") as file_in:    lines = []    for line in file_in:        lines.append(line)


matomo