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inspect.signautre: Fix functools.partial support. Issue #21117
This commit is contained in:
Yury Selivanov
parent
1d1d95bf83
commit
3f73ca23cf
3 changed files with 146 additions and 97 deletions
137
Lib/inspect.py
137
Lib/inspect.py
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@ -1518,7 +1518,8 @@ def _signature_get_partial(wrapped_sig, partial, extra_args=()):
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on it.
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"""
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new_params = OrderedDict(wrapped_sig.parameters.items())
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old_params = wrapped_sig.parameters
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new_params = OrderedDict(old_params.items())
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partial_args = partial.args or ()
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partial_keywords = partial.keywords or {}
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@ -1532,32 +1533,57 @@ def _signature_get_partial(wrapped_sig, partial, extra_args=()):
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msg = 'partial object {!r} has incorrect arguments'.format(partial)
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raise ValueError(msg) from ex
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for arg_name, arg_value in ba.arguments.items():
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param = new_params[arg_name]
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if arg_name in partial_keywords:
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# We set a new default value, because the following code
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# is correct:
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#
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# >>> def foo(a): print(a)
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# >>> print(partial(partial(foo, a=10), a=20)())
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# 20
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# >>> print(partial(partial(foo, a=10), a=20)(a=30))
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# 30
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#
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# So, with 'partial' objects, passing a keyword argument is
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# like setting a new default value for the corresponding
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# parameter
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#
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# We also mark this parameter with '_partial_kwarg'
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# flag. Later, in '_bind', the 'default' value of this
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# parameter will be added to 'kwargs', to simulate
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# the 'functools.partial' real call.
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new_params[arg_name] = param.replace(default=arg_value,
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_partial_kwarg=True)
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elif (param.kind not in (_VAR_KEYWORD, _VAR_POSITIONAL) and
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not param._partial_kwarg):
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new_params.pop(arg_name)
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transform_to_kwonly = False
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for param_name, param in old_params.items():
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try:
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arg_value = ba.arguments[param_name]
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except KeyError:
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pass
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else:
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if param.kind is _POSITIONAL_ONLY:
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# If positional-only parameter is bound by partial,
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# it effectively disappears from the signature
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new_params.pop(param_name)
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continue
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if param.kind is _POSITIONAL_OR_KEYWORD:
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if param_name in partial_keywords:
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# This means that this parameter, and all parameters
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# after it should be keyword-only (and var-positional
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# should be removed). Here's why. Consider the following
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# function:
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# foo(a, b, *args, c):
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# pass
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#
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# "partial(foo, a='spam')" will have the following
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# signature: "(*, a='spam', b, c)". Because attempting
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# to call that partial with "(10, 20)" arguments will
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# raise a TypeError, saying that "a" argument received
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# multiple values.
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transform_to_kwonly = True
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# Set the new default value
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new_params[param_name] = param.replace(default=arg_value)
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else:
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# was passed as a positional argument
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new_params.pop(param.name)
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continue
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if param.kind is _KEYWORD_ONLY:
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# Set the new default value
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new_params[param_name] = param.replace(default=arg_value)
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if transform_to_kwonly:
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assert param.kind is not _POSITIONAL_ONLY
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if param.kind is _POSITIONAL_OR_KEYWORD:
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new_param = new_params[param_name].replace(kind=_KEYWORD_ONLY)
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new_params[param_name] = new_param
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new_params.move_to_end(param_name)
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elif param.kind in (_KEYWORD_ONLY, _VAR_KEYWORD):
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new_params.move_to_end(param_name)
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elif param.kind is _VAR_POSITIONAL:
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new_params.pop(param.name)
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return wrapped_sig.replace(parameters=new_params.values())
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@ -2103,7 +2129,7 @@ class Parameter:
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`Parameter.KEYWORD_ONLY`, `Parameter.VAR_KEYWORD`.
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"""
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__slots__ = ('_name', '_kind', '_default', '_annotation', '_partial_kwarg')
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__slots__ = ('_name', '_kind', '_default', '_annotation')
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POSITIONAL_ONLY = _POSITIONAL_ONLY
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POSITIONAL_OR_KEYWORD = _POSITIONAL_OR_KEYWORD
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@ -2113,8 +2139,7 @@ class Parameter:
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empty = _empty
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def __init__(self, name, kind, *, default=_empty, annotation=_empty,
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_partial_kwarg=False):
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def __init__(self, name, kind, *, default=_empty, annotation=_empty):
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if kind not in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD,
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_VAR_POSITIONAL, _KEYWORD_ONLY, _VAR_KEYWORD):
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@ -2139,17 +2164,13 @@ class Parameter:
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self._name = name
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self._partial_kwarg = _partial_kwarg
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def __reduce__(self):
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return (type(self),
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(self._name, self._kind),
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{'_partial_kwarg': self._partial_kwarg,
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'_default': self._default,
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{'_default': self._default,
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'_annotation': self._annotation})
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def __setstate__(self, state):
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self._partial_kwarg = state['_partial_kwarg']
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self._default = state['_default']
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self._annotation = state['_annotation']
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@ -2169,8 +2190,8 @@ class Parameter:
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def kind(self):
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return self._kind
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def replace(self, *, name=_void, kind=_void, annotation=_void,
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default=_void, _partial_kwarg=_void):
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def replace(self, *, name=_void, kind=_void,
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annotation=_void, default=_void):
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"""Creates a customized copy of the Parameter."""
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if name is _void:
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@ -2185,11 +2206,7 @@ class Parameter:
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if default is _void:
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default = self._default
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if _partial_kwarg is _void:
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_partial_kwarg = self._partial_kwarg
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return type(self)(name, kind, default=default, annotation=annotation,
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_partial_kwarg=_partial_kwarg)
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return type(self)(name, kind, default=default, annotation=annotation)
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def __str__(self):
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kind = self.kind
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@ -2215,17 +2232,6 @@ class Parameter:
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id(self), self)
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def __eq__(self, other):
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# NB: We deliberately do not compare '_partial_kwarg' attributes
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# here. Imagine we have a following situation:
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#
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# def foo(a, b=1): pass
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# def bar(a, b): pass
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# bar2 = functools.partial(bar, b=1)
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#
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# For the above scenario, signatures for `foo` and `bar2` should
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# be equal. '_partial_kwarg' attribute is an internal flag, to
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# distinguish between keyword parameters with defaults and
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# keyword parameters which got their defaults from functools.partial
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return (issubclass(other.__class__, Parameter) and
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self._name == other._name and
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self._kind == other._kind and
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@ -2265,12 +2271,7 @@ class BoundArguments:
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def args(self):
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args = []
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for param_name, param in self._signature.parameters.items():
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if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or
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param._partial_kwarg):
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# Keyword arguments mapped by 'functools.partial'
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# (Parameter._partial_kwarg is True) are mapped
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# in 'BoundArguments.kwargs', along with VAR_KEYWORD &
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# KEYWORD_ONLY
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if param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY):
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break
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try:
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@ -2295,8 +2296,7 @@ class BoundArguments:
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kwargs_started = False
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for param_name, param in self._signature.parameters.items():
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if not kwargs_started:
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if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or
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param._partial_kwarg):
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if param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY):
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kwargs_started = True
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else:
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if param_name not in self.arguments:
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@ -2378,18 +2378,14 @@ class Signature:
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name = param.name
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if kind < top_kind:
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msg = 'wrong parameter order: {} before {}'
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msg = 'wrong parameter order: {!r} before {!r}'
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msg = msg.format(top_kind, kind)
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raise ValueError(msg)
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elif kind > top_kind:
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kind_defaults = False
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top_kind = kind
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if (kind in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD) and
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not param._partial_kwarg):
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# If we have a positional-only or positional-or-keyword
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# parameter, that does not have its default value set
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# by 'functools.partial' or other "partial" signature:
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if kind in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD):
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if param.default is _empty:
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if kind_defaults:
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# No default for this parameter, but the
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@ -2570,15 +2566,6 @@ class Signature:
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parameters_ex = ()
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arg_vals = iter(args)
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if partial:
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# Support for binding arguments to 'functools.partial' objects.
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# See 'functools.partial' case in 'signature()' implementation
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# for details.
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for param_name, param in self.parameters.items():
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if (param._partial_kwarg and param_name not in kwargs):
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# Simulating 'functools.partial' behavior
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kwargs[param_name] = param.default
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while True:
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# Let's iterate through the positional arguments and corresponding
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# parameters
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