I am trying to implement slice functionality for a class I am making that creates a vector representation.
I have this code so far, which I believe will properly implement the slice but whenever I do a call like v[4]
where v is a vector python returns an error about not having enough parameters. So I am trying to figure out how to define the getitem
special method in my class to handle both plain indexes and slicing.
def __getitem__(self, start, stop, step):
index = start
if stop == None:
end = start + 1
else:
end = stop
if step == None:
stride = 1
else:
stride = step
return self.__data[index:end:stride]
The __getitem__()
method will receive a slice
object when the object is sliced. Simply look at the start
, stop
, and step
members of the slice
object in order to get the components for the slice.
>>> class C(object):
... def __getitem__(self, val):
... print val
...
>>> c = C()
>>> c[3]
3
>>> c[3:4]
slice(3, 4, None)
>>> c[3:4:-2]
slice(3, 4, -2)
>>> c[():1j:'a']
slice((), 1j, 'a')