Question

Some stated that python dictionary is thread safe. Does it mean I can or cannot modify the items in a dictionary while iterating over it?

Answer 1

The two concepts are completely different. Thread safety means that two threads cannot modify the same object at the same time, thereby leaving the system in an inconsistent state.

That said, you cannot modify a dictionary while iterating over it. See the documentation..

The dictionary p should not be mutated during iteration. It is safe (since Python 2.1) to
modify the values of the keys as you iterate over the dictionary, but only so long as the
set of keys does not change.