python - Converting List into Dictionary of Sorted Tuples

Question

I've used the following approach many times to generate a list of tuples from the contents of a dictionary:

dispositions = list(dispositions.items())

In this case, the keys are different types of ways a patient can leave the emergency department, and the values are counts of those types. Now, I wanted to sort this data based on the second item in each of the tuples, so I tried this:

dispositions = list(dispositions.items()).sort(key=lambda x: x[1])

To my surprise, when I ran the code, I found that dispositions had been set to None. I tried breaking it into two parts, as follows:

dispositions = list(dispositions.items())
dispositions.sort(key=lambda x: x[1])

This works! I got my list of sorted tuples. So, I've already solved my problem, but I want to know why the first option didn't work so that I can be a better person (better programmers are better people). Can anyone help me out here?

question from:https://stackoverflow.com/questions/65909352/converting-list-into-dictionary-of-sorted-tuples

Answer 1

list.sort does not return anything. So this:

dispositions = list(dispositions.items()).sort(key=lambda x: x[1])

sets dispositions to None.

sorted on the other hand returns a new list. So you would use:

dispositions = sorted(dispositions.items(), key=lambda x: x[1])

Which will set dispositions to a sorted list of tuples.