On Tue, 2017-06-27 at 04:54 -0500, Larry Evans wrote:
> The following code:
>
> --{--cut here--
> #Purpose:
> # Demonstrate class with __add__ and __mult__ methods
> # to demonstrate shortestPath calculations.
> #OriginalSource:
> # ./shortestPath.py
> #References:
> # [1]
> http://www.marinamele.com/2014/04/modifying-add-method-of-python-clas
> s.html
> # [2]
> https://docs.scipy.org/doc/numpy/reference/c-api.types-and-structures
> .html#c.PyArray_Descr
> # [3]
> https://www.abebooks.com/book-search/title/graphs-networks/author/car
> re-bernard/
> # Table 3.1, path algebra P2.
> # [4] https://docs.python.org/3/library/abc.html
> ###########################################
> import numpy as np
> from abc import ABCMeta, abstractmethod
> class PathAbstract(metaclass=ABCMeta):
> @abstractmethod
> def __repr__(self):
> pass
> @abstractmethod
> def __add__(self, other):
> pass
> @abstractmethod
> def __radd__(self, other):
> pass
> @abstractmethod
> def __mul__(self, other):
> pass
> @abstractmethod
> def __rmul__(self, other):
> pass
>
> class ShortestNull(PathAbstract):
> '''Null object in ShortestPath algebra[3]'''
> def __str__(self):
> return "<0>"
> def __repr__(self):
> return self.__str__()
> def __addreal__(self, other):
> return other
> def __add__(self, other):
> return other
> def __radd__(self, other):
> return other
> def __mulreal__(self, other):
> return self
> def __mul__(self, other):
> return self
> def __rmul__(self, other):
> return self
>
> class ShortestUnit(PathAbstract):
> '''Unit object in ShortestPath algebra[3]'''
> def __str__(self):
> return "<1>"
> def __repr__(self):
> return self.__str__()
> def __addreal__(self, other):
> return self
> def __add__(self, other):
> return self
> def __radd__(self, other):
> return self
> def __mulreal__(self, other):
> return other
> def __mul__(self, other):
> return other
> def __rmul__(self, other):
> return other
>
> class ShortestPath(PathAbstract):
> def __init__(self, distance):
> self.distance = distance
> def __str__(self):
> return "{0:4.1f}".format(self.distance)
> def __repr__(self):
> return self.__str__()
> def __addreal__(self, other):
> #paths composed of following shortest of self path or other
> path.
> min_dist=min(self.distance,other.distance)
> return ShortestPath(min_dist)
> def __add__(self, other):
> #paths composed of following shortest of self path or other
> path.
> if(other == 0):
> n=ShortestNull()
> return n.__addreal__(self)
> else:
> return other.__addreal__(self)
> def __radd__(self, other):
> return self.__add__(other)
> def __mulreal__(self, other):
> #path composed of self path followed by other path.
> min_dist=self.distance+other.distance
> return ShortestPath(min_dist)
> def __mul__(self, other):
> return other.__mulreal__(self)
> def __rmul__(self, other):
> return other.__mulreal__(self)
>
>
> d0=ShortestNull()
> d1=ShortestUnit()
> d2=ShortestPath(3)
> d3=ShortestPath(6)
> print(' d0=',d0,' d1=',d1,' d2=',d2,' d3=',d3)
> print(' type(d0)=',type(d0).__name__)
> d4=d0+d2+d3
> print('d4=',d4)
> d5=d2*d3
> print('d5=',d5)
> d6=d0*d2
> print('d6=',d6)
> d7=d1*d2
> print('d7=',d7)
> d8=d2*d0
> print('d8=',d8)
> d9=d2*d1
> print('d9=',d9)
> a=np.array([[ShortestNull,ShortestPath(12)],[ShortestPath(12),Shortes
> tNull()]],dtype=object)
> print('a=',a,sep='\n')
> print('a[0]=',a[0],sep='\n')
> print('a[0][0]=',a[0][0],sep='\n')
> #a00mul=a[0][0]*a[0][0]
> a00mul=a[0][0].__mul__(a[0][0])
> print('a00mul=',a00mul,sep='\n')
> #at=a.transpose()
> #print('at=',at,sep='\n')
> #aat=a.dot(at)
> print('aat=',aat,sep='\n')
> #mp=np.matmul(a,at)#this gives error about Object arrays not
> supported.
> #print('mp=',mp)
> --}--cut here--
>
>
> When run by make, gives this result:
>
>
> --{--cut here--
> make -k
> python3 shortestPathABC.py
> d0= <0> d1= <1> d2= 3.0 d3= 6.0
> type(d0)= ShortestNull
> d4= 3.0
> d5= 9.0
> d6= <0>
> d7= 3.0
> d8= <0>
> d9= 3.0
> a=
> [[<class '__main__.ShortestNull'> 12.0]
> [12.0 <0>]]
> a[0]=
> [<class '__main__.ShortestNull'> 12.0]
> a[0][0]=
> <class '__main__.ShortestNull'>
> Traceback (most recent call last):
> File "shortestPathABC.py", line 123, in <module>
> a00mul=a[0][0].__mul__(a[0][0])
> TypeError: __mul__() missing 1 required positional argument: 'other'
> Makefile:7: recipe for target 'all' failed
> make: *** [all] Error 1
> --}--cut here--
>
> I don't understand why. Apparently, a[0][0] is not a ShortestNull
> because otherwise, the .__mul__ would have the positional argument,
> 'other' equal to a[0][0].
> I don't think debugging support really suits the list, but.... how about you see why in your result: [[<class '__main__.ShortestNull'> 12.0] [12.0 <0>]] a[0, 0] and a[1, 1] do not show up as the same thing? - Sebastian > What am I missing? > > TIA. > > -regards, > Larry > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion >
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