I'm trying to read a text file with matrix and put it in a list, but I am using two loops here and I want my function to be faster.

def read_file(path_to_file):
    for eachLine in open(path_to_file,'rt'):
        mylist.append([int(eachRow) for eachRow in eachLine.split()])
    return mylist
  • \$\begingroup\$ Since the result will be a list of lists and int can handle only one number at a time, you have to have 2 loops of some sort. \$\endgroup\$
    – hpaulj
    Commented Mar 15, 2016 at 1:37

1 Answer 1


Not sure if it's possible to make this faster. But it can be better:

with open(path_to_file, 'rt') as fh:
    return [[int(value) for value in line.split()] for line in fh]

First of all, you should always use a with ... context manager when working with files. That way you cannot forget to close the file handle after you are done reading from it.

Other improvements:

  • More natural variable names
  • Simpler and more compact writing style using a list comprehension

Also keep in mind PEP8, the Python style guide.


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