Lists

[buran]

Don't modify list while iterating over it.

How to remove items from a list while iterating?

In your case you can construct working_config directly with list comprehension, while iterating over config. i.e. no need to create copy and then remove elements from it

working_config = [item for item in config if "GigabitEthernet" in item]

Note, there is one more problem - because row is a tuple (due to using enumerate) where first element is row index, and the second element - string resulting from splitting lines in the file, I would expect no elements will be removed.

Could you provide sample config file in full (i.e. not full content but how it looks unmodified)

---

Finally, you may want to have on third-party package like https://pypi.org/project/ciscoconfparse/