custom dict that allows delete during iteration

Question

UPDATED based on Lennart Regebro\'s answer

Suppose you iterate through a dictionary, and sometimes need to delete an element. The following is very efficient:

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Answer 1

Python 3.2 has such dict in the stdlib:

#!/usr/bin/env python3
from collections import OrderedDict as odict

d = odict(zip(range(3), "abc"))
print(d)
for k in d:
    if k == 2:
       del d[k]
print(d)

Output

OrderedDict([(0, 'a'), (1, 'b'), (2, 'c')])
OrderedDict([(0, 'a'), (1, 'b')])

Iteration is performed over a linked list, see __iter__() method implementation. The deletion is safe (in Python 3.2) even though items are weak references.