Python – 保留出现 N 次 K 的记录

有时，在使用Python元组列表时，我们可能会遇到一个问题，即我们需要保留所有出现 K 次的记录。此类问题可能出现在 Web 开发和日常编程等领域。让我们讨论可以执行此任务的某些方式。

Input : test_list = [(4, 5, 5, 4), (5, 4, 3)], K = 5, N = 2 
Output : [(4, 5, 5, 4)]
Input : test_list = [(4, 5, 5, 4), (5, 4, 3)], K = 5, N = 3 
Output : [] 
 

方法 #1：使用列表理解 + count()
上述功能的组合可以用来解决这个问题。在此，我们使用列表推导执行计算出现次数和条件以及迭代的任务。

Python3

# Python3 code to demonstrate working of
# Retain records with N occurrences of K
# Using count() + list comprehension
 
# initializing list
test_list = [(4, 5, 6, 4, 4), (4, 4, 3), (4, 4, 4), (3, 4, 9)]
 
# printing original list
print("The original list is : " + str(test_list))
 
# initializing K
K = 4
 
# initializing N
N = 3
 
# Retain records with N occurrences of K
# Using count() + list comprehension
res = [ele for ele in test_list if ele.count(K) == N]
 
# printing result
print("Filtered tuples : " + str(res))

输出 ：

The original list is : [(4, 5, 6, 4, 4), (4, 4, 3), (4, 4, 4), (3, 4, 9)]
Filtered tuples : [(4, 5, 6, 4, 4), (4, 4, 4)]

方法 #2：使用列表理解 + sum()
上述功能的组合可以用来解决这个问题。在此，我们使用 sum() 执行计算 K 的总和计数的任务。

Python3

# Python3 code to demonstrate working of
# Retain records with N occurrences of K
# Using list comprehension + sum()
 
# initializing list
test_list = [(4, 5, 6, 4, 4), (4, 4, 3), (4, 4, 4), (3, 4, 9)]
 
# printing original list
print("The original list is : " + str(test_list))
 
# initializing K
K = 4
 
# initializing N
N = 3
 
# Retain records with N occurrences of K
# Using list comprehension + sum()
res = [ele for ele in test_list if sum(cnt == K for cnt in ele) == N]
 
# printing result
print("Filtered tuples : " + str(res))

输出 ：

The original list is : [(4, 5, 6, 4, 4), (4, 4, 3), (4, 4, 4), (3, 4, 9)]
Filtered tuples : [(4, 5, 6, 4, 4), (4, 4, 4)]