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Python Python Collections (Retired) Lists Redux Manipulating Lists

Kody Dibble
Kody Dibble
2,554 Points
Posted by Kody Dibble
Kody Dibble
2,554 Points

Python Challenge .extend

Not sure how to use the .extend method correctly.

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

# Your code goes below here

the_list.pop(3)
the_list.insert(0, 1)

the_list.remove("a")
del the_list[1:7]

the_list.extend(range(0, 21))
Richard Lu
Richard Lu
20,185 Points
Richard Lu
Richard Lu
20,185 Points

extend(...) L.extend(iterable) -- extend list by appending elements from the iterable

That's what it shows when you do a help(list.extend). It basically means you can concatenate another iterable object (i.e. string, list) onto the list. If I'm not wrong you could do this:

the_list.extend("myotheriterableobject")

2 Answers

Jason Anello
PLUS
Jason Anello
Courses Plus Student 94,610 Points
Jason Anello
Jason Anello
Courses Plus Student 94,610 Points

Hi Kody,

We should first back up to task 2 because you've deleted more items than you should have and this will affect the answer for task 3.

After removing the 'a' the list would look like [1, 2, 3, False, [1, 2, 3]] At this point you only need to remove the boolean False and the list that comes after it.

With your del statement you're removing a slice of the list that begins at index 1 and goes past the end of the list(last valid index is 4).

All this leaves you with is [1] and you needed [1, 2, 3] It still passed the challenge but it shouldn't have been allowed.

So you need to fix the slice so that it starts at the index where the False is and goes to the end.

At this point you should have the list [1, 2, 3] when you start task 3.

Task 3 wants a list of all the numbers from 1 to 20. You already have 1, 2, 3 so you simply need to extend it by the numbers that are missing.

So you'll need to adjust the starting number on your range function in this code: the_list.extend(range(0, 21))

Iain Simmons
MOD
Iain Simmons
Treehouse Moderator 32,305 Points
Iain Simmons
Iain Simmons
Treehouse Moderator 32,305 Points

The last challenge task asks you to make the list contain the numbers 1 through 20. It should already have 1, 2, and 3.

As Xing Hui Lu points out, extend will concatenate another iterable on to the end of the one you call it on.

So you need to extend the the_list iterable with another one containing the numbers 4 through 20. You can use the range method, but you'll need to adjust the parameters to get the numbers you need.