python - 如何在Python中便宜地获取大文件的行数？(How to get line count of a large file cheaply in Python?)

Question

I need to get a line count of a large file (hundreds of thousands of lines) in python.

(我需要在python中获取一个大文件（数十万行）的行数。)

What is the most efficient way both memory- and time-wise?

(内存和时间最有效的方法是什么？)

At the moment I do:

(目前，我这样做：)

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?

(有可能做得更好吗？)

  ask by SilentGhost translate from so

Answer 1

一行，可能非常快：

num_lines = sum(1 for line in open('myfile.txt'))