Regarding the problem of counting the number of different numerical types in a list of integers in Python.

Question

In the following code, kind_num is used to count the integers with several different values ​​in the integer list.

class Solution(object):
    def distributeCandies(self, candies):
        """
        :type candies: List[int]
        :rtype: int
        """
        loc = len(candies)
        mol = loc % 2
        if not (2 <= loc <= 10000) or mol != 0:
            return 'wrong length of array'
        for num in candies:
            if not (-10000 <= num <= 10000):
                return 'wrong element in array'

        kind_num = 0
        sis_num = loc / 2
        for candy in candies:
            kind_num += 1
            while True:
                try:
                    candies.remove(candy)
                    print candies
                except ValueError:
                    break
        if kind_num > sis_num:
            return sis_num
        elif kind_num < sis_num:
            return kind_num
        else:
            return sis_num


s = Solution()

print s.distributeCandies([1,1,2,2,3,3])

But the second for loop exited early before completing the values ​​in the candies. Why is this? ? ?

Answer 1

Don’t remove in the loop

If you just want to count different types of values

#统计出现次数
lst = [1,1,2,2,3,3,4,4,5,6]
print len(set(lst))

#统计每种各出现几次
from collections import Counter
print dict(Counter(lst))

Answer 2

candies.remove(candy) is executed for the first time Ok, candy is removed; due to while (True), this candy will be removed infinitely in the same For loop, but this candy has been removed the first time. So break.

Answer 3

from collections import defaultdict

d = defaultdict(int)

for item in your_list:
    d[item] += 1
    
print d