How to get line count cheaply in Python?

Question

I need to get a line count of a large file (hundreds of thousands of lines) in python. What is the most efficient way both memory- and time-wise? At the moment I do: def file_len(fname): with open(fname) as f: for i, l in enumerate(f): pass return i + 1 is it possible to do any better? Select the correct answer from above options

Answer 1

The fastest and one-liner, a solution which is also an efficient way to count lines and it takes less memory and time is as follows:- num_lines = sum(1 for line in open('myfile.txt'))