Python supports LSP, does it?
roy at panix.com
Wed Aug 10 05:06:42 CEST 2005
Andy Leszczynski <leszczynscyATnospam.yahoo.com.nospam> writes:
> Is not LSP more a quality of the desing of class hierachy rather then
> language itslef? Comments?
I do agree that LSP is more a class hierarchy thing than a language thing.
For example, it's easy in Python to write a LSP-violating set of classes:
print "I am base"
class child (base):
f = "not a function"
Since you can call base.f(), LSP says you should also be able to call
child.f(). Well, I suppose you can, but most people would not consider
throwing a TypeError to satisfy the LSP :-).
Mike Meyer <mwm at mired.org> wrote:
> It's not a true statement. Nothing in the language enforces LSP. In
> fact, there's not even a [way?] when a function/method is invoked to make
> sure the type passed in is a subtype of the type you expect
Well, that's not entirely true. I could write:
def func (self, obj):
assert (isinstance (obj, baseClass))
It's sort of un-pythonic, but the language certainly lets you do it if you
really want to.
More information about the Python-list