How to remove item when looping through a list in Python

The best way is to make a copy of the list first. Like this:

words = ['xaa', 'sss', 'aaa', 'bbb']
for word in words[:]:
    if word[0] == 'x':
      words.remove(word)

At first, I use code like this to achieve my goal:

words = ['xaa', 'aaa', 'bbb', 'ccc']
for word in words:
  if word[0] == 'x':
    words.remove(word)

the behavior of this code is not ensured. Thera are some other ways to modify a list while looping through the list. But I stick to the copy method.