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Python Python Collections (Retired) Lists Redux Manipulating Lists

Meg Seegmiller
Meg Seegmiller
15,150 Points
Posted by Meg Seegmiller
Meg Seegmiller
15,150 Points

When I submit task 1, it passes; but after adding my code for task 2, I receive an error that Task 1 no longer passes

When I submit task 1, it passes; but after adding my code for task 2, I receive an error that Task 1 no longer passes even though no changes have been made to the code for Task 1. Help!

1st Challenge:

Move the 1 to position 0. You can do this in one step with .pop() and .insert().

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))

2nd Challenge:

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

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))

i=0
for item in the_list:
  del the_list[i]
  the_list.remove(item)
  i+=1
  del the_list[i]

del the_list

2 Answers

karis hutcheson
karis hutcheson
7,036 Points

It's because, in the second section of your code, you basically delete everything in the list. So the checker looks for "1" to be in position "0" and doesn't find it. It then stops looking and says that task one no longer passes. Technically, both challenges are failing.

What he's basically asking for is to remove indexes 1, 4 and 5 (after the move) which correspond to the "a", False and [1,2,3] list. You can either accomplish this by using del to delete their indexes (not a great method, but it will pass you):

del the_list[5]
del the_list[4]
del the_list[1]

or using .remove() to get them (better way):

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

Remember, when using the del method: I did them from last index to first because Python parses code one line at a time. Meaning that if you del [1] first, all of the other items' indexes change where 2 becomes 1, 3 becomes 2 and so forth.

What you did in your for loop was to go through every item and delete them. You ended with an empty list, then called del the_list which killed the variable in memory too.

Meg Seegmiller
Meg Seegmiller
15,150 Points
Meg Seegmiller
Meg Seegmiller
15,150 Points

This is what I get for trying to do the code challenge late at night! I was reading the question as removing all the items from the list rather than just the three the challenge lists.

And thank you for explaining how my errors in challenge two affected challenge one.

karis hutcheson
karis hutcheson
7,036 Points

No prob! :)

Ken Alger
STAFF
Ken Alger
Treehouse Teacher
Ken Alger
Ken Alger
Treehouse Teacher

Megan;

Typically when the challenge engine errors out like that it means there is a syntax error occurring preventing it from working at all.

Having said that, I posted a response on this same challenge earlier today. Take a look and see if it helps.

Happy coding,

Ken