Safely appending to a key's value list

Often when working with dictionaries, you will need to initialize a data type before you can use it. A prime example of this is a list, which has to be initialized on each key before you can append to that list.

A defaultdict allows you to define what each uninitialized key will contain. When establishing a defaultdict, you pass it the type you want it to be, such as a list, tuple, set, int, string, dictionary or any other valid type object.

You'll be working with the same weight log as last exercise, but with the male penguins in our study.

Import defaultdict from collections.
Create a defaultdict with a default type of list called male_penguin_weights.
Iterate over the list weight_log, unpacking it into the variables species, sex, and body_mass, as you did in the previous exercise. Use species as the key of the male_penguin_weights dictionary and append body_mass to its value.
Print the first 2 items of the male_penguin_weights dictionary. You can use the .items() method for this. Remember to make it a list.

Exercise

Safely appending to a key's value list

Instructions