Deprecate psutil.NUM_CPUS and introduce cpu_count()

[giampaolo]

From g.rodola on December 03, 2013 19:08:28

Reasons to deprecate it
=======================

- it's calculated at import time, also unnecessarily if the user does not use it later

- import time is risky: if the retrieval fails for some reason the whole 
program will explode (see for example issue 188 ). Right now we alleviate the 
problem by catching the exception and produce a warning but it's sub optimal.


Replacement
===========

- a new psutil.cpu_count() can be introduced

- that will also be consistent with os.cpu_count() introduced in python 3.4 
http://docs.python.org/3.4/library/os.html#os.cpu_count - it paves the way for 
upcoming psutil.phys_cpu_count() (see issue 427 )


Deprecation process
===================

Deprecation of a module level constant is harder than deprecating a function 
because it's more tricky: 
http://stackoverflow.com/questions/9937279/can-modules-have-properties 
http://stackoverflow.com/questions/880530/can-python-modules-have-properties-the-same-way-that-objects-can
 I expect to introduce the "module property" hack in some next version (say 
1.3.0) which will produce a DeprecationWarning and remove it completely in a 
major one (say 2.0.0) along with others already deprecated APIs such as 
psutil.BOOT_TIME.

Original issue: http://code.google.com/p/psutil/issues/detail?id=450

[giampaolo]

From g.rodola on December 03, 2013 13:38:01

Status: Duplicate
Mergedinto: 451