Strange assignment behavior with dictionary in nested loops

Question

So I need to rearrange some values in my dictionary. Specifically, for 'Verb', the list comes before 'verb three', and I'd like it to come right after. I'm trying to use the foo[i], foo[j] = foo[j], foo[i] swapping method on a dummy list which I'll then assign over the original. Like so:

test_dict = {'Noun': ['noun one', 'noun two', 'noun three'], 
             'Verb': ['verb one', 'verb two', ['list one', 'list two',
                      'list three'], 'verb three', 'verb four']}

e = test_dict

for key in sorted(e):
    fixed_list = e[key]
    print('    ', key)
    for i in range(0, len(e[key])):
        print(i)
        print(type(e[key][i]))    
        if type(e[key][i]) == list:  
            print('ooh, this one\'s a list!', e[key][i])
            print('   and here it is in fixed_list: ', fixed_list[i])
            fixed_list[i], fixed_list[i+1] = fixed_list[i+1], fixed_list[i]
    e[key] = fixed_list

However, the bizarre output I get is [Note: the list in my 'Verb' key will never come last, so ignore the IndexError]:

 Noun
0
<class 'str'>
1
<class 'str'>
2
<class 'str'>

 Verb
0
<class 'str'>
1
<class 'str'>
2
<class 'list'>
ooh, this one's a list! ['list one', 'list two', 'list three']
and here it is in fixed_list:  ['list one', 'list two', 'list three']
3
<class 'list'>
ooh, this one's a list! ['list one', 'list two', 'list three']
and here it is in fixed_list:  ['list one', 'list two', 'list three']
4
<class 'list'>
ooh, this one's a list! ['list one', 'list two', 'list three']
and here it is in fixed_list:  ['list one', 'list two', 'list three']
Traceback (most recent call last):
File "/home/ubuntu/workspace/my_project.py", line 567, in <module>
fixed_list[i], fixed_list[i+1] = fixed_list[i+1], fixed_list[i]
IndexError: list index out of range

Now, unless I'm crazy, it seems like reassigning elements of fixed_list is causing issues in the key's value list inside the inner loop, but how? The only time they 'touch' each other assignment-wise is at the beginning and end of the outer loop.

`fixed_list = e[key]` does not create a copy. All you did is create another reference to the same list object. You are then altering the list you are already iterating over. — Martijn Pieters, Oct 25 '17 at 15:37
@depperm: so? They sorted the keys, and are only handling the lists, which *are* ordered. — Martijn Pieters, Oct 25 '17 at 15:37
@depperm: yes, and both are objects in a list. Which has ordering. — Martijn Pieters, Oct 25 '17 at 15:38
Mostly unrelated but you can use `isinstance(obj, list)`. Direct comparison with `type(obj)` is *sometimes* correct if you know what you're doing, but is generally an anti-pattern. — Iguananaut, Oct 25 '17 at 15:39
@MartijnPieters that would explain the behavior, thank you very much for solving my head-scratcher. — Luke McPuke, Oct 25 '17 at 15:40
@Iguananaut thanks for the tip; not certain what 'anti-pattern' entails, but I'll take your word for it and make it more correct. — Luke McPuke, Oct 25 '17 at 15:43

Strange assignment behavior with dictionary in nested loops

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