Python|两个或多个列表的并集

列表的并集意味着，我们必须从列表 A 和列表 B 中取出所有元素（可以有两个以上的列表）并将它们放入一个新列表中。有多种顺序可以组合列表。例如，我们可以保持重复和顺序或删除最终列表中的重复元素等。
例子：

Maintained repetition only
Input : 
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
Output :
[23, 15, 2, 14, 14, 16, 20, 52, 2, 48, 
15, 12, 26, 32, 47, 54]

Maintained repetition and order
Input : 
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
Output :
[2, 2, 12, 14, 14, 15, 15, 16, 20, 23, 
26, 32, 47, 48, 52, 54]

Without repetition
Input : 
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
Output :
[32, 2, 12, 14, 15, 16, 48, 47, 20, 52, 54, 23, 26]

Union of three lists
Input : 
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
lst3 = [4, 78, 5, 6, 9, 25, 64, 32, 59]
Output :
[32, 64, 2, 4, 5, 6, 9, 12, 14, 15, 16, 
48, 47, 78, 20, 52, 54, 23, 25, 26, 59]

保持重复

我们可以简单地使用加号“+”运算符将两个列表合二为一。这将反映重复。

# Python program to illustrate union
# Maintained repetition 
def Union(lst1, lst2):
    final_list = lst1 + lst2
    return final_list
  
# Driver Code
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
print(Union(lst1, lst2))

输出：

[23, 15, 2, 14, 14, 16, 20, 52, 2, 48, 15, 
12, 26, 32, 47, 54]

保持重复和秩序

为了保持新列表中出现的顺序，我们需要使用sorted()函数，将两个列表的相加（加上操作，如上一个问题）作为参数传递。

# Python program to illustrate union
# Maintained repetition and order 
def Union(lst1, lst2):
    final_list = sorted(lst1 + lst2)
    return final_list
  
# Driver Code
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
print(Union(lst1, lst2))

输出：

[2, 2, 12, 14, 14, 15, 15, 16, 20, 23, 26, 32, 47, 48, 52, 54]

不重复

为了摆脱初始列表中的所有重复元素，我们分别在两个列表上使用set()函数。然后我们使用“+”运算符添加它们并作为新列表传递。

# Python program to illustrate union
# Without repetition 
def Union(lst1, lst2):
    final_list = list(set(lst1) | set(lst2))
    return final_list
  
# Driver Code
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
print(Union(lst1, lst2))

输出：

[32, 2, 12, 14, 15, 16, 48, 47, 20, 
52, 54, 23, 26]

两个以上的列表

我们还可以合并两个以上的列表。这可以通过同时使用set() 和 union()函数来有效地完成，如下例所示。这也照顾重复并防止它们。

# Python program to illustrate union
# Union of three lists
def Union(lst1, lst2, lst3):
    final_list = list(set().union(lst1, lst2, lst3))
    return final_list
  
# Driver Code
lst1 = [23, 15, 2, 14, 14, 16, 20 ,52]
lst2 = [2, 48, 15, 12, 26, 32, 47, 54]
lst3 = [4, 78, 5, 6, 9, 25, 64, 32, 59]
print(Union(lst1, lst2, lst3))

输出：

[32, 64, 2, 4, 5, 6, 9, 12, 14, 15, 16, 
48, 47, 78, 20, 52, 54, 23, 25, 26, 59]