Import txt file and having each line as a list

Question

I'm a new Python user.

I have a txt file that will be something like:

3,1,3,2,3
3,2,2,3,2
2,1,3,3,2,2
1,2,2,3,3,1
3,2,1,2,2,3

but may be less or more lines.

I want to import each line as a list.

I know you can do it as such:

filename = 'MyFile.txt' 
fin=open(filename,'r')
L1list = fin.readline()
L2list = fin.readline()
L3list = fin.readline()

but since I don't know how many lines I will have, is there another way to create individual lists?

Answer 1

Do not create separate lists; create a list of lists:

results = []
with open('inputfile.txt') as inputfile:
    for line in inputfile:
        results.append(line.strip().split(','))

or better still, use the csv module:

import csv

results = []
with open('inputfile.txt', newline='') as inputfile:
    for row in csv.reader(inputfile):
        results.append(row)

Lists or dictionaries are far superiour structures to keep track of an arbitrary number of things read from a file.

Note that either loop also lets you address the rows of data individually without having to read all the contents of the file into memory either; instead of using results.append() just process that line right there.

Just for completeness sake, here's the one-liner compact version to read in a CSV file into a list in one go:

import csv

with open('inputfile.txt', newline='') as inputfile:
    results = list(csv.reader(inputfile))