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# 28.3. `__builtin__` — Built-in objects

This module provides direct access to all ‘built-in’ identifiers of Python; for example, `__builtin__.open` is the full name for the built-in function `open()`. See 内置函数 and 内置常量 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 __builtin__

    def open(path):
        f = __builtin__.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()

        # ...

CPython implementation detail: Most modules have the name `__builtins__` (note the `'s'`) made available as part of their globals. The value of `__builtins__` is normally either this module or the value of this modules’s `__dict__` attribute. Since this is an implementation detail, it may not be used by alternate implementations of Python.