[Python-Dev] .pyc file has different result for value "1.79769313486232e+308" than .py file

Dino Viehland dinov at exchange.microsoft.com
Wed Sep 13 20:05:32 CEST 2006


We've noticed a strange occurance on Python 2.4.3 w/ the floating point value 1.79769313486232e+308 and how it interacts w/ a .pyc.  Given x.py:

def foo():
        print str(1.79769313486232e+308)
        print str(1.79769313486232e+308) == "1.#INF"


The 1st time you run this you get the correct value, but if you reload the module after a .pyc is created then you get different results (and the generated byte code appears to have changed).

Python 2.4.3 (#69, Mar 29 2006, 17:35:34) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import x
>>> import dis
>>> dis.dis(x.foo)
  2           0 LOAD_GLOBAL              0 (str)
              3 LOAD_CONST               1 (1.#INF)
              6 CALL_FUNCTION            1
              9 PRINT_ITEM
             10 PRINT_NEWLINE

  3          11 LOAD_GLOBAL              0 (str)
             14 LOAD_CONST               1 (1.#INF)
             17 CALL_FUNCTION            1
             20 LOAD_CONST               2 ('1.#INF')
             23 COMPARE_OP               2 (==)
             26 PRINT_ITEM
             27 PRINT_NEWLINE
             28 LOAD_CONST               0 (None)
             31 RETURN_VALUE
>>> reload(x)
<module 'x' from 'x.pyc'>
>>> dis.dis(x.foo)
  2           0 LOAD_GLOBAL              0 (str)
              3 LOAD_CONST               1 (1.0)
              6 CALL_FUNCTION            1
              9 PRINT_ITEM
             10 PRINT_NEWLINE

  3          11 LOAD_GLOBAL              0 (str)
             14 LOAD_CONST               1 (1.0)
             17 CALL_FUNCTION            1
             20 LOAD_CONST               2 ('1.#INF')
             23 COMPARE_OP               2 (==)
             26 PRINT_ITEM
             27 PRINT_NEWLINE
             28 LOAD_CONST               0 (None)
             31 RETURN_VALUE
>>> ^Z


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