En Tue, 06 Jan 2009 06:56:36 -0200, James Stroud <jstr...@mbi.ucla.edu>
escribió:
Steven Woody wrote:
On Tue, Jan 6, 2009 at 4:42 PM, James Stroud <jstr...@mbi.ucla.edu>
wrote:
py> import __builtin__
py> __builtin__.abs is abs
True
Does that mean someone did 'import * from __builtin__' when python
startup?
In terms of the exact implementation of the cPython interpreter, I don't
know. But the interpreter behaves as if someone did just that. So there
is nothing wrong with thinking of it this way if it helps you understand
the interpreter.
Not exactly. Built-in names are "one step further" global names; it's not
that builtin names populate by default the global namespace. As local
names "hide" (or "shadow") global names, those global names "hide" builtin
names. Those three namespaces are distinct, like onion layers (global and
local namespaces are the same at the module level).
If the interpreter did the equivalent of "from __builtin__ import *",
redefining builtin names would destroy them, but that's not the case:
# the builtin "abs" function
abs(-3)
3
abs
<built-in function abs>
# this one "hides" the builtin abs
def abs(x):
... return "Hi, I'm the abs() global function!"
...
abs(-3)
"Hi, I'm the abs() global function!"
abs
<function abs at 0x00B9F2F0>
# remove the global "abs"
del abs
# we can access again the builtin "abs"
abs(-3)
3
abs
<built-in function abs>
--
Gabriel Genellina
--
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