问题
Possible Duplicate:
while (1) Vs. for while(True) — Why is there a difference?
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.
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.
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
回答1:
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" # :-(
Luckily, in python 3.2 I get SyntaxError: assignment to keyword.
来源：https://stackoverflow.com/questions/8953439/while-true-or-while-1