The best answers to the question “How to read a file line-by-line into a list?” in the category Dev.
How do I read every line of a file in Python and store each line as an element in a list?
I want to read the file line by line and append each line to the end of the list.
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 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)
This will yield an “array” of lines from the file.
lines = tuple(open(filename, 'r'))
open returns a file which can be iterated over. When you iterate over a file, you get the lines from that file.
tuple can take an iterator and instantiate a tuple instance for you from the iterator that you give it.
lines is a tuple created from the lines of the file.
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)