如何在 Python 3 中使用 cmp()?

问题描述

我无法让命令 cmp() 工作.

I cannot get the command cmp() to work.

代码如下:

a = [1,2,3]
b = [1,2,3]
c = cmp(a,b)
print (c)

我收到错误:

Traceback (most recent call last):
  File "G:\Dropbox\Code\a = [1,2,3]", line 3, in <module>
    c = cmp(a,b)
 NameError: name 'cmp' is not defined
[Finished in 0.1s]

推荐答案

正如评论中提到的，cmp 在 Python 3 中不存在.如果你真的想要它，你可以自己定义它:

As mentioned in the comments, cmp doesn't exist in Python 3. If you really want it, you could define it yourself:

def cmp(a, b):
    return (a > b) - (a < b)

取自原始 Python 3.0 的新功能.不过，这种情况非常罕见——尽管并非闻所未闻——但确实需要它，因此您可能需要考虑这是否真的是做任何事情的最佳方式.

which is taken from the original What's New In Python 3.0. It's pretty rare -- though not unheard of -- that it's really needed, though, so you might want to think about whether it's actually the best way to do whatever it is you're up to.

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