00001 """Robust apply mechanism
00002
00003 Provides a function "call", which can sort out
00004 what arguments a given callable object can take,
00005 and subset the given arguments to match only
00006 those which are acceptable.
00007 """
00008 __version__ = "$Revision: 2.1 $"
00009
00010 def function( receiver ):
00011 """Get function-like callable object for given receiver
00012
00013 returns (function_or_method, codeObject, fromMethod)
00014
00015 If fromMethod is true, then the callable already
00016 has its first argument bound
00017 """
00018 if hasattr(receiver, '__call__'):
00019 # receiver is a class instance; assume it is callable.
00020 # Reassign receiver to the actual method that will be called.
00021 if hasattr( receiver.__call__, 'im_func') or hasattr( receiver.__call__, 'im_code'):
00022 receiver = receiver.__call__
00023 if hasattr( receiver, 'im_func' ):
00024 # an instance-method...
00025 return receiver, receiver.im_func.func_code, 1
00026 elif not hasattr( receiver, 'func_code'):
00027 raise ValueError('unknown reciever type %s %s'%(receiver, type(receiver)))
00028 return receiver, receiver.func_code, 0
00029
00030 def robustApply(receiver, *arguments, **named):
00031 """Call receiver with arguments and an appropriate subset of named
00032 """
00033 receiver, codeObject, startIndex = function( receiver )
00034 acceptable = codeObject.co_varnames[startIndex+len(arguments):codeObject.co_argcount]
00035 for name in codeObject.co_varnames[startIndex:startIndex+len(arguments)]:
00036 if named.has_key( name ):
00037 raise TypeError(
00038 """Argument %r specified both positionally and as a keyword for calling %r"""% (
00039 name, receiver,
00040 )
00041 )
00042 if not (codeObject.co_flags & 8):
00043 # fc does not have a **kwds type parameter, therefore
00044 # remove unacceptable arguments.
00045 for arg in named.keys():
00046 if arg not in acceptable:
00047 del named[arg]
00048 return receiver(*arguments, **named)
00049
00050
