(Python) Can someone help me with what I have wrong in my code?-CodePudding

The objective is to return the multiple of three that occurs within a string. I only have to worry about the multiples 3,6,9 and use a dictionary. For example, 0939639 would return 9 since it appeared 3 times while the other multiple of three appeared less than that.

Here is my code:

def count_threes(n):
    # Turning the number into a string
    x = len(str(n))

    # Setting the keys(multiple of threes) to 0 as the default count
    dict = {3: 0,
            6: 0,
            9: 0}

    # Loop through the string. If the number is a multiple of 3, it increments the key's value.
    for el in n:
        num = int(el)
        if num % 3 == 0 and num != 0:
            dict[el]  = 1

    # Gets the maximum value and returns the key
    max_val = max(dict, key=dict.get)
    return max_val

I do have a given test file to test the function on. I keep getting a KeyError so it's having a hard time pulling the key. I can't seem to figure out where in my code is wrong.

CodePudding user response：

Your dict contains int as key, and el is a string, so you can't find it in the dict, use num to access the dict

Also, don't name it dict that is the dictionary constructor keyword, and you can use a defaultdict that saves you to write initial values

from collections import defaultdict

def count_threes(value):
    counter = defaultdict(int)
    for char in value:
        num = int(char)
        if num and num % 3 == 0:
            counter[num]  = 1

    return max(counter, key=counter.get)

print(count_threes('09396390000'))  # 9

CodePudding user response：

You just need to change:

    dict[el]  = 1

to:

    dict[num]  = 1

The dict keys are integers, not strings, so you need to use the integer value, num, as the key.

CodePudding user response：

There were the following issues in the code:

you should refrain from keeping dictionary names as the actual datatype (you kept it as dict)
you took the len of the number which wasn't required, we just had to convert it to a string
you were looping through n and not x, and we can't loop through an integer using "in" keyword
the key you were using was the string of "el", i.e which was looping through x, you had to keep the key as num

def count_threes(n):
    # Turning the number into a string
    x = str(n)

    # Setting the keys(multiple of threes) to 0 as the default count
    _dict = {3: 0,
            6: 0,
            9: 0}

    # Loop through the string. If the number is a multiple of 3, it increments the key's value.
    for el in x:
        num = int(el)
        if num % 3 == 0 and num != 0:
            _dict[num]  = 1

    # Gets the maximum value and returns the key
    max_val = max(_dict, key=_dict.get)
    return max_val