29.3. "builtins" --- Built-in objects
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This module provides direct access to all 'built-in' identifiers of
Python; for example, "builtins.open" is the full name for the built-in
function "open()".  See 內建函式 and 內建常數 for documentation.

This module is not normally accessed explicitly by most applications,
but can be useful in modules that provide objects with the same name
as a built-in value, but in which the built-in of that name is also
needed.  For example, in a module that wants to implement an "open()"
function that wraps the built-in "open()", this module can be used
directly:

   import builtins

   def open(path):
       f = builtins.open(path, 'r')
       return UpperCaser(f)

   class UpperCaser:
       '''Wrapper around a file that converts output to upper-case.'''

       def __init__(self, f):
           self._f = f

       def read(self, count=-1):
           return self._f.read(count).upper()

       # ...

As an implementation detail, most modules have the name "__builtins__"
made available as part of their globals.  The value of "__builtins__"
is normally either this module or the value of this module's
"__dict__" attribute. Since this is an implementation detail, it may
not be used by alternate implementations of Python.
