In Python, you might come across the error message “dictionary changed size during iteration”, when you’re trying to modify a dictionary while also iterating over it.

Here’s an analogy: imagine you’re walking down a street (iterating) and all of a sudden the city starts demolishing buildings or constructing new ones (modifying the street/dictionary) simultaneously. This could lead to a lot of confusion. You might end up in the wrong place or you might even face a dead end (encounter an error).

Contrary to many opinions, I’d say that sometimes, certain situations might require changing the dictionary size during iteration. But to avoid this error, you should create a copy of the dictionary for iteration, and make changes to the original one. This will involve more memory usage, which might not be ideal in all situations.