Python - 列表中匹配元素的计数（包括重复项）

给定 2 个列表，计算两个列表中所有相似的元素，包括重复的。

Input : test_list1 = [3, 5, 6, 7, 2, 3, 5], test_list2 = [5, 5, 3, 9, 8, 5]
Output : 4
Explanation : 3 repeats 2 times, and 5 two times, totalling to 4.

Input : test_list1 = [3, 5, 6], test_list2 = [5, 3, 9]
Output : 2
Explanation : 3 repeats 1 time, and 5 one time, totalling to 2.

方法#1：使用循环

这是可以执行此任务的粗暴方式。在这种情况下，我们在迭代一个列表的同时迭代另一个列表的每个元素，并增加计数器。

Python3

# Python3 code to demonstrate working of 
# Count of matching elements among lists [ Including duplicates ]
# Using loop
  
# initializing lists
test_list1 = [3, 5, 6, 7, 2, 3]
test_list2 = [5, 5, 3, 9, 8]
  
# printing original lists
print("The original list 1 : " + str(test_list1))
print("The original list 2 : " + str(test_list2))
  
# using loop to iterate each element
res = 0
for ele in test_list1:
    if ele in test_list2:
        res += 1
  
# printing result 
print("All matching elements : " + str(res))

输出

The original list 1 : [3, 5, 6, 7, 2, 3]
The original list 2 : [5, 5, 3, 9, 8]
All matching elements : 3

方法 #2：使用 sum() + 生成器表达式

上述方法的结合就是用来解决这个问题的。在此，我们使用 sum() 对元素进行计数，生成器表达式执行迭代任务。

Python3

# Python3 code to demonstrate working of 
# Count of matching elements among lists [ Including duplicates ]
# Using sum() + generator expression
  
# initializing lists
test_list1 = [3, 5, 6, 7, 2, 3]
test_list2 = [5, 5, 3, 9, 8]
  
# printing original lists
print("The original list 1 : " + str(test_list1))
print("The original list 2 : " + str(test_list2))
  
# using sum to count occurrences
res = sum(ele in test_list1 for ele in test_list2)
  
# printing result 
print("All matching elements : " + str(res))

输出

The original list 1 : [3, 5, 6, 7, 2, 3]
The original list 2 : [5, 5, 3, 9, 8]
All matching elements : 3