Dictionaries homework

[ichabod801]

As nilamo and Gribouillis said, you shouldn't modify the list you are looping through. It's also bad to delete from a list that was passed to a function. This will change the list outside the function, which may not be expected. To avoid having the same pair in the list twice, you should check before appending (word, rev_word) to new_lst to make sure that (rev_word, word) isn't already in new_lst.