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"""
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A context manager for managing things injected into :mod:`builtins`.
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"""
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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import builtins as builtin_mod
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from traitlets.config.configurable import Configurable
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from traitlets import Instance
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class __BuiltinUndefined(object): pass
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BuiltinUndefined = __BuiltinUndefined()
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class __HideBuiltin(object): pass
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HideBuiltin = __HideBuiltin()
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class BuiltinTrap(Configurable):
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shell = Instance('IPython.core.interactiveshell.InteractiveShellABC',
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allow_none=True)
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def __init__(self, shell=None):
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super(BuiltinTrap, self).__init__(shell=shell, config=None)
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self._orig_builtins = {}
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# We define this to track if a single BuiltinTrap is nested.
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# Only turn off the trap when the outermost call to __exit__ is made.
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self._nested_level = 0
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self.shell = shell
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# builtins we always add - if set to HideBuiltin, they will just
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# be removed instead of being replaced by something else
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self.auto_builtins = {'exit': HideBuiltin,
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'quit': HideBuiltin,
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'get_ipython': self.shell.get_ipython,
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}
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def __enter__(self):
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if self._nested_level == 0:
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self.activate()
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self._nested_level += 1
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# I return self, so callers can use add_builtin in a with clause.
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return self
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def __exit__(self, type, value, traceback):
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if self._nested_level == 1:
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self.deactivate()
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self._nested_level -= 1
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# Returning False will cause exceptions to propagate
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return False
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def add_builtin(self, key, value):
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"""Add a builtin and save the original."""
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bdict = builtin_mod.__dict__
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orig = bdict.get(key, BuiltinUndefined)
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if value is HideBuiltin:
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if orig is not BuiltinUndefined: #same as 'key in bdict'
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self._orig_builtins[key] = orig
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del bdict[key]
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else:
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self._orig_builtins[key] = orig
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bdict[key] = value
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def remove_builtin(self, key, orig):
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"""Remove an added builtin and re-set the original."""
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if orig is BuiltinUndefined:
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del builtin_mod.__dict__[key]
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else:
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builtin_mod.__dict__[key] = orig
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def activate(self):
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"""Store ipython references in the __builtin__ namespace."""
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add_builtin = self.add_builtin
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for name, func in self.auto_builtins.items():
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add_builtin(name, func)
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def deactivate(self):
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"""Remove any builtins which might have been added by add_builtins, or
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restore overwritten ones to their previous values."""
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remove_builtin = self.remove_builtin
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for key, val in self._orig_builtins.items():
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remove_builtin(key, val)
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self._orig_builtins.clear()
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self._builtins_added = False
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