在 Python 中， read() 或 readlines() 更快吗? [英] In Python, is read() , or readlines() faster?

问题描述

我想在我的代码中读取一个大文件.read() 或 readline() 为此更快.循环如何:

I want to read a huge file in my code. Is read() or readline() faster for this. How about the loop:

for line in fileHandle

推荐答案

对于文本文件，只需使用 for 循环遍历它几乎总是可行的方法.别在意速度，它是最干净的.

For a text file just iterating over it with a for loop is almost always the way to go. Never mind about speed, it is the cleanest.

在某些版本的 python readline() 确实只读取一行，而 for 循环读取大块并将它们分成几行，所以它可能更快.我认为更新版本的 Python 也对 readline() 使用缓冲，因此性能差异将是微不足道的(for 可能仍然在微观上更快，因为它避免了方法调用).然而，出于性能原因选择一种而不是另一种可能是过早的优化.

In some versions of python readline() really does just read a single line while the for loop reads large chunks and splits them up into lines so it may be faster. I think that more recent versions of Python use buffering also for readline() so the performance difference will be minuscule (for is probably still microscopically faster because it avoids a method call). However choosing one over the other for performance reasons is probably premature optimisation.

编辑添加:我刚刚查看了一些 Python 发行说明.Python 2.5 说:

Edit to add: I just checked back through some Python release notes. Python 2.5 said:

现在混合迭代是非法的文件中带有 for 行的文件和调用文件对象的read()/readline()/readlines() 方法.

It’s now illegal to mix iterating over a file with for line in file and calling the file object’s read()/readline()/readlines() methods.

Python 2.6 引入了 TextIOBase，它同时支持迭代和 readline().

Python 2.6 introduced TextIOBase which supports both iterating and readline() simultaneously.

Python 2.7 固定交错 read() 和 readline().

Python 2.7 fixed interleaving read() and readline().

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