要讀取個大文件，文件大概是3G左右，擔心read會出現內存溢出的情況，網上找了個靠譜的用法：

with open(...) as f:
    for line in f:
        <do something with line>

The with statement handles opening and closing the file, including if an exception is raised in the inner block. The for line in f treats the file object f as an iterable, which automatically uses buffered IO and memory management so you don‘t have to worry about large files.

There should be one -- and preferably only one -- obvious way to do it.

python 讀取大文件