109 lines
3.7 KiB
Python
109 lines
3.7 KiB
Python
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# -*- coding: utf-8 -*-
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"""
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Created on Mon Jan 13 18:17:15 2014
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@author: takluyver
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"""
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import sys
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PY3 = (sys.version_info[0] >= 3)
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try:
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from inspect import signature, Parameter # Python >= 3.3
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except ImportError:
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from ._signatures import signature, Parameter
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if PY3:
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from functools import wraps
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else:
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from functools import wraps as _wraps
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def wraps(f):
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def dec(func):
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_wraps(f)(func)
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func.__wrapped__ = f
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return func
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return dec
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def callback_prototype(prototype):
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"""Decorator to process a callback prototype.
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A callback prototype is a function whose signature includes all the values
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that will be passed by the callback API in question.
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The original function will be returned, with a ``prototype.adapt`` attribute
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which can be used to prepare third party callbacks.
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"""
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protosig = signature(prototype)
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positional, keyword = [], []
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for name, param in protosig.parameters.items():
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if param.kind in (Parameter.VAR_POSITIONAL, Parameter.VAR_KEYWORD):
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raise TypeError("*args/**kwargs not supported in prototypes")
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if (param.default is not Parameter.empty) \
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or (param.kind == Parameter.KEYWORD_ONLY):
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keyword.append(name)
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else:
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positional.append(name)
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kwargs = dict.fromkeys(keyword)
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def adapt(callback):
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"""Introspect and prepare a third party callback."""
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sig = signature(callback)
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try:
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# XXX: callback can have extra optional parameters - OK?
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sig.bind(*positional, **kwargs)
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return callback
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except TypeError:
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pass
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# Match up arguments
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unmatched_pos = positional[:]
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unmatched_kw = kwargs.copy()
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unrecognised = []
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# TODO: unrecognised parameters with default values - OK?
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for name, param in sig.parameters.items():
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# print(name, param.kind) #DBG
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if param.kind == Parameter.POSITIONAL_ONLY:
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if len(unmatched_pos) > 0:
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unmatched_pos.pop(0)
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else:
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unrecognised.append(name)
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elif param.kind == Parameter.POSITIONAL_OR_KEYWORD:
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if (param.default is not Parameter.empty) and (name in unmatched_kw):
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unmatched_kw.pop(name)
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elif len(unmatched_pos) > 0:
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unmatched_pos.pop(0)
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else:
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unrecognised.append(name)
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elif param.kind == Parameter.VAR_POSITIONAL:
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unmatched_pos = []
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elif param.kind == Parameter.KEYWORD_ONLY:
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if name in unmatched_kw:
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unmatched_kw.pop(name)
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else:
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unrecognised.append(name)
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else: # VAR_KEYWORD
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unmatched_kw = {}
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# print(unmatched_pos, unmatched_kw, unrecognised) #DBG
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if unrecognised:
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raise TypeError("Function {!r} had unmatched arguments: {}".format(callback, unrecognised))
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n_positional = len(positional) - len(unmatched_pos)
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@wraps(callback)
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def adapted(*args, **kwargs):
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"""Wrapper for third party callbacks that discards excess arguments"""
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# print(args, kwargs)
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args = args[:n_positional]
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for name in unmatched_kw:
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# XXX: Could name not be in kwargs?
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kwargs.pop(name)
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# print(args, kwargs, unmatched_pos, cut_positional, unmatched_kw)
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return callback(*args, **kwargs)
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return adapted
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prototype.adapt = adapt
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return prototype
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