Antoon Pardon wrote: > That depends on whether the programmes wants value equality > or identity equality. > > In the first case the programmer shouldn't mutate a after > it was introduced as key in the dictionary; but should > either introduce a copy or work on a copy later. As > such your snippet of code would become. > > a = [1,2,3] > d[a[:]] = 9 > a.append(4) > print d[a] > > And this would raise a KeyError, unless the list [1,2,3,4] > would be in the dictionary. > > In the second case your code would produce 9.
how does the dictionary know if you want key value equality or key identity equality? </F> -- http://mail.python.org/mailman/listinfo/python-list
