How to remove items from a list while iterating?

Question

I'm iterating over a list of tuples in Python, and am attempting to remove them if they meet certain criteria. for tup in somelist: if determine(tup): code_to_remove_tupWhat should I use in place of `code_to_remove_tup`? I can't figure out how to remove the item in this fashion.

Answer 1

You should not remove data from a structure over which you are iterating. Removing the current data may disrupt the __next__() function and prevent the for loop from reaching the raising of StopIteration which results in an infinite loop.

Instead you have two options.

First, you can iterate over a range that is the length of the list of tuples, but you must use a while loop and each time that you remove a tuple be sure to subtract 1 from the index to account for the change to the structure. This is the most memory efficient method.

Second, instead of removing tuple you can copy the other tuples to a new list. This would be a great place to use list comprehension.

I'm happy to help guide you through this process.