Question

I have a nested list:

a = [[{'aa': 2L}, {}, {'mm': 9L}, {}, {}], [{'aa': 1L}, {}, {'mm': 5L}, {}, {}], [{'aa': 2L}, {}, {'mm': 7L}, {}, {}], [{'aa': 5L}, {}, {'mm': 7L}, {}, {}]]

Desired Output:

a = [[{'aa': 1L}, {}, {'mm': 5L}, {}, {}], [{'aa': 2L}, {}, {'mm': 7L}, {}, {}], [{'aa': 5L}, {}, {'mm': 7L}, {}, {}], [{'aa': 2L}, {}, {'mm': 9L}, {}, {}]]

Output I am getting from a.sort() :

a = [[{'aa': 1L}, {}, {'mm': 5L}, {}, {}], [{'aa': 2L}, {}, {'mm': 7L}, {}, {}], [{'aa': 2L}, {}, {'mm': 9L}, {}, {}], [{'aa': 5L}, {}, {'mm': 7L}, {}, {}]]

Not desired.

Here I want to sort the list ‘a’ by considering any one of the keys of child lists.In this case I am using third dictionary and key ‘mm’.Right now there is only one key ‘mm’ there may be multiple key value pairs but I should be able to avoid others and do the sorting on the basis of ‘mm’ keys value only.

Answer 1

I am not sure if I got the question correctly, but the answer seems simple to me as below.

Index the third item [3] in the key and then re-index the dictionary with key mm

>>> sorted(a,key=lambda key:key[2]['mm'])
[[{'aa': 1L}, {}, {'mm': 5L}, {}, {}], [{'aa': 2L}, {}, {'mm': 7L}, {}, {}], [{'aa': 5L}, {}, {'mm': 7L}, {}, {}], [{'aa': 2L}, {}, {'mm': 9L}, {}, {}]]
>>>