是True还是1？ [英] While True or while 1?

问题描述

可能重复：

我有时在其他人中看到 1，而不是 while True。
我认为使用True更像是pythonic，但我想检查
在实践中是否有任何区别。

I see sometimes in other people code "while 1" instead of "while True". I think using True is more pythonic, but I wanted to check if there is any difference in practice.

所以我尝试了随后，结果令人惊讶。对于
，我可以看到它看起来像解释器可以优化1布尔值
转换，而没有使用True，这与我
的假设相反。

So I tried to do the following, and the result is surprising. For what I can see it looks like the interpreter can optimize away the 1 boolean conversion while it doesn't with the True, the opposite of what I supposed.

任何人都可以解释我为什么会这样，或者我的结论错了吗？

Anyone can explain me why is that, or maybe is my conclusion wrong?

def f1():
    while 1:
        pass

def f2():
    while True:
        pass

In [10]: dis.dis(f)
2           0 SETUP_LOOP               3 (to 6)

3     >>    3 JUMP_ABSOLUTE            3
      >>    6 LOAD_CONST               0 (None)
            9 RETURN_VALUE

In [9]: dis.dis(f1)
2           0 SETUP_LOOP              10 (to 13)
      >>    3 LOAD_GLOBAL              0 (True)
            6 POP_JUMP_IF_FALSE       12

3           9 JUMP_ABSOLUTE            3
      >>   12 POP_BLOCK
      >>   13 LOAD_CONST               0 (None)
           16 RETURN_VALUE

推荐答案

编译器无法优化对 True 的引用，因为不幸的是，在python 2中，我可以这样做：

The compiler can't optimize away the reference to True because, unfortunately, in python 2 I can do this:

True = []
if not True:
    print "oops" # :-(

幸运的是，在python 3.2中，我得到 SyntaxError：分配给关键字。

Luckily, in python 3.2 I get SyntaxError: assignment to keyword.

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