Legs under a log

A class turned over logs in a garden and recorded each animal it found, with its phylum and its number of legs. You will total the legs of the arthropods, count the animals of each phylum, and draw a bar chart.

The idea. Each record is a tuple: the name, the phylum and the number of legs. Animals without legs have $0$.

Your tasks.

1. Set arthropod_legs to the total number of legs of the arthropods.
2. In count_by_phylum, return a dictionary from each phylum to the number of animals in it.
3. Set legless to a list of the names of the animals with no legs, in the order of the records.