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while True or while 1

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  while True or while 1 Andrea Crotti <andrea.crotti.0@gmail.com> - 2012-01-21 13:47 +0000
    Re: while True or while 1 Erik Max Francis <max@alcyone.com> - 2012-01-21 13:14 -0800

#19188 — while True or while 1

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

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#19195

Andrea Crotti wrote:
> 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.

No (with the exception of `True` and `False` being rebinable in Python 
2).  The idiomatic `while 1` notation comes from back in the pre-Boolean 
days.  In any reasonably modern implementation, `while True` is more 
self-documenting.  I would imagine the primary reason people still do 
it, any after-the-fact rationalizations aside, is simply habit.

-- 
Erik Max Francis && max@alcyone.com && http://www.alcyone.com/max/
  San Jose, CA, USA && 37 18 N 121 57 W && AIM/Y!M/Jabber erikmaxfrancis
   Ambition can creep as well as soar.
    -- Edmund Burke

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