Function to sort a list in a specific order, while also counting the amount of times each value appe-CodePudding

So I need to define a function that returns a list that is arranged in a specific order, and also gives the amount of times each value appears.

For example, let's say i have this input:

["s", "w", "h", "s", "h"]

I'll need my function to return this:

[2, 2, 1]

The 2 is the amount of times s appears, the following 2 is the amount of times h appears, and the 1 is the amount of times w appears.

I have been stuck on this for quite a while now, this is how far I came:

def item_order(list):
    sort_order = {"s": 0, "h": 1, "w": 2}
    list.sort(key=lambda val: sort_order[val[1]])

But I'm not sure if this is the right way to go. Any help would be greatly appreciated!

CodePudding user response：

You can use collections.Counter to count number of items. For example:

from collections import Counter


def item_order(lst):
    weights = {"s": 0, "h": 1, "w": 2}
    rv = sorted(lst, key=weights.get)
    return rv, Counter(rv)


lst = ["s", "w", "h", "s", "h"]
sorted_list, cnt = item_order(lst)
print(sorted_list)
print(cnt)  # or list(cnt.values())

Prints:

['s', 's', 'h', 'h', 'w']
Counter({'s': 2, 'h': 2, 'w': 1})

CodePudding user response：

# A set for values already seen
seen_characters = set()

# Function sorts a list of characters, calculates count of unique characters
# Parameter:    list -> of characters
# Returns:   list -> of numbers 
def item_order(character_list):
    result = []
    character_list.sort()
    for character in character_list:
        if character not in seen_characters:
            result.append(character_list.count(character))
            seen_characters.add(character)
    return result

given_list = ['s', 'w', 'h', 's', 'h']
print(item_order(given_list))