什么是'不'的'pythonic' [英] What is more 'pythonic' for 'not'

问题描述

我已经看过两种方式，但哪种方式更像Pythonic？

I have seen it both ways, but which way is more Pythonic?

a = [1, 2, 3]

# version 1
if not 4 in a:
    print 'is the not more pythonic?'

# version 2
if 4 not in a:
    print 'this haz more engrish'

将考虑哪种方式更好的Python？

Which way would be considered better Python?

推荐答案

第二个选项更多Pythonic有两个原因：

The second option is more Pythonic for two reasons:

• 它是一个运算符，转换为一个字节码操作数。另一行真的是而不是（4 in a）;两个运营商。

• It is one operator, translating to one bytecode operand. The other line is really not (4 in a); two operators.

碰巧， Python 优化后一种情况并将 not（x in y）转换为 x而不是y无论如何，，但这是CPython编译器的一个实现细节。

As it happens, Python optimizes the latter case and translates not (x in y) into x not in y anyway, but that is an implementation detail of the CPython compiler.

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