Python|从整数列表中打印重复项的程序

给定一个包含重复元素的整数列表。生成另一个列表的任务，其中仅包含重复的元素。简单来说，新列表应该包含出现多个的元素。

例子 ：

Input : list = [10, 20, 30, 20, 20, 30, 40, 50, -20, 60, 60, -20, -20]
Output : output_list = [20, 30, -20, 60]


Input :  list = [-1, 1, -1, 8]
Output : output_list = [-1]

方法 1：使用蛮力方法

Python3

# Python program to print
# duplicates from a list
# of integers
def Repeat(x):
    _size = len(x)
    repeated = []
    for i in range(_size):
        k = i + 1
        for j in range(k, _size):
            if x[i] == x[j] and x[i] not in repeated:
                repeated.append(x[i])
    return repeated
 
# Driver Code
list1 = [10, 20, 30, 20, 20, 30, 40,
         50, -20, 60, 60, -20, -20]
print (Repeat(list1))
     
# This code is contributed
# by Sandeep_anand

输出 ：

[20, 30, -20, 60]

方法 2：使用收集模块中的 Counter()函数

Python3

from collections import Counter
 
l1 = [1,2,1,2,3,4,5,1,1,2,5,6,7,8,9,9]
d = Counter(l1)
print(d)
 
new_list = list([item for item in d if d[item]>1])
print(new_list)

输出

Counter({1: 4, 2: 3, 5: 2, 9: 2, 3: 1, 4: 1, 6: 1, 7: 1, 8: 1})
[1, 2, 5, 9]

方法 3：使用 count() 方法

Python3

# program to print duplicate numbers in a given list
# provided input
list = [1,2,1,2,3,4,5,1,1,2,5,6,7,8,9,9] 
 
new = []  # defining output list
 
# condition for reviewing every
# element of given input list
for a in list: 
 
      # checking the occurrence of elements
    n = list.count(a) 
     
    # if the occurrence is more than
    # one we add it to the output list
    if n > 1:        
 
        if new.count(a) == 0:  # condition to check
 
            new.append(a)
 
print(new)
 
# This code is contributed by Himanshu Khune

输出：

[1, 2, 5, 9]