[Python] How to avoid "RuntimeError: dictionary changed size during iteration" error?

Suppose I have a dictionary of lists:

d = {'a': [1], 'b': [1, 2], 'c': [], 'd':[]}


Now I want to remove key-value pairs where the values are empty lists. I tried this code:

for i in d:
if not d:
d.pop(i)


but this gives an error:

RuntimeError: dictionary changed size during iteration


I understand that entries can't be added or removed from a dictionary while iterating through it. How can I work around this limitation in order to solve the problem?


See Modifying a Python dict while iterating over it for citations that this can cause problems, and why.

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