Python on Unix:
>>> sys.version_info (2, 5, 1, 'final', 0) >>> print float('nan') nanPython on Windows:
>>> print sys.version_info (2, 5, 1, 'final', 0) >>> print float('nan') Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: invalid literal for float(): nanWhile documentation says 'nan' feature should be available only in 2.6.