How does list comprehension with an `if` clause work?

Question

How does the max_list variable list comprehension work?

def mode(*args):
    dict_vals = {i: args.count(i) for i in args}
    max_list = [k for k, v in dict_vals.items() if v == max(dict_vals.values())]
    return max_list

I know that the dict_vals creates a dictionary that holds onto the values you enter (the key) and the number of occurrences for each value (the value of the key). I also know that max_list creates a list of the keys (values) that occur the most based on the being the maximum value (occurrence). I am just wanting to know how the comprehension used in max_list works and maybe some other examples of turning dictionaries into lists with similar syntax for useful applications. Also, is there similar ways to do this with tuples?

Answer 1

dict_vals.items()

The items() method yields each key-value pair in the dictionary.

k, v in dict_vals.items()

This iterates over each key-value pair in the dictionary yielded by items()

k, v in dict_vals.items() if v == max(dict_vals.values())

This filters that list of key-value pairs by selecting only those pairs where the value is equal to maximum in value stored in the dict_vals (.values() gives you all the values & max() finds the largest among those).

Finally,

k for k,v in dict_vals.items() if v == max(dict_vals.values())

Selects only the key (k) for those pairs. The [] makes it a list.