<s>[INST] How to get line count cheaply in Python? 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?
 [/INST] One line, probably pretty fast:
num_lines = sum(1 for line in open('myfile.txt'))

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