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Python Python Collections (Retired) Lists Redux Manipulating Lists

Taro Tiankanon
Taro Tiankanon
2,208 Points
Posted by Taro Tiankanon
Taro Tiankanon
2,208 Points

Need clarification on this .remove() problem

The question asked to:

Use .remove() and/or del to remove the string, boolean, and list members of the_list.

And my code is the following...

I'm wondering why the list data type ([1,2,3]) is still on the list after this for loop?

lists.py 
the_list = ["a", 2, 3, 1, False, [1, 2, 3]]

# Your code goes below here
the_list.insert(0,the_list.pop(3))

for value in the_list:
  if type(value) is list or type(value) is bool or type(value) is str:
    the_list.remove(value)
Alexander Davison
Alexander Davison
65,469 Points

So I'd do this instead, which is much simpler:

the_list.remove("a")
the_list.remove(False)
the_list.remove([1, 2, 3])

Hope that helps! ~xela888

1 Answer

Steven Parker
Steven Parker
230,274 Points
Steven Parker
Steven Parker
230,274 Points

Python gets confused when you remove items from the set that controls the loop. In this case, the loop is ending prematurely and last item is never seen. You can avoid this peculiarity by making sure your loop uses a copy of the list you will be modifying:

for value in the_list[:]: