What makes functions special?

Eric Snow ericsnowcurrently at gmail.com
Sat Jul 9 17:28:58 EDT 2011

A tracker issue [1] recently got me thinking about what makes
functions special.  The discussion there was regarding the distinction
between compile time (generation of .pyc files for modules and
execution of code blocks), [function] definition time, and [function]
execution time.  Definition time actually happens during compile time,
but it has its own label to mark the contrast with execution time.  So
why do functions get this special treatment?

Functions are a special case in Python for providing a more optimized
execution of a code block in pure Python code.  And how is that?  When
the function is defined, a code object is generated for the function
body along with a few "static" details that will be used during
execution.  No other objects have code objects.  No other objects in
Python have this special optimization.

Maybe I am missing something, or maybe it is super obvious, but isn't
this a critical point?  Is it just a CPython implementation detail
that code objects should provide an optimization, or is it a
specification of the language?   From the docs, the code objects in of
function objects are the latter, but the optimization expectation is
not clearly indicated.  Are there other motivations behind code
objects that I am missing?  Am I wrong about the optimization



[1] http://bugs.python.org/issue12374

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