用列表中的第 j 个元素交换第 i 个元素的Python程序

给定一个列表，任务是将Python程序写入给定的元素列表，切换列表中的每个 i 和 j 元素。

例子：

Input : test_list = [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4], i, j = 4, 8 
Output : [8, 7, 4, 0, 4, 8, 2, 9, 8, 4, 8] 
Explanation : 4 is swapped by 8 at each occurrence.

Input : test_list = [4, 7, 8, 0, 8, 4], i, j = 4, 8 
Output : [8, 7, 4, 0, 4, 8] 
Explanation : 4 is swapped by 8 at each occurrence. 
 

方法一：使用循环+条件语句

在此，我们使用条件 if-else 语句执行切换任务，并使用循环执行迭代任务。

Python3

# Python3 code to demonstrate working of
# Toggle i,j elements in List
# Using loop + conditional statements
  
# initializing list
test_list = [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
               
# printing original list
print("The original list is : " + str(test_list))
  
# initializing i, j 
i, j = 4, 8
  
for idx in range(len(test_list)):
      
    # perform toggling
    if int(test_list[idx]) == i:
        test_list[idx] = j
    elif int(test_list[idx]) == j:
        test_list[idx] = i
          
# printing result
print("The altered list : " + str(test_list))

输出：

The original list is : [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
The altered list : [8, 7, 4, 0, 4, 8, 2, 9, 8, 4, 8]

方法二：使用列表推导+外部函数

在此，我们使用外部切换函数执行切换任务，并使用列表理解来遍历列表。

蟒蛇3

# Python3 code to demonstrate working of
# Toggle i,j elements in List
# Using list comprehension + external function
  
# external toggle 
def toggle(ele, i, j):
  
    # performing toggle
    if ele == i:
        return j
    elif ele == j:
        return i
    return ele
  
# initializing list
test_list = [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
               
# printing original list
print("The original list is : " + str(test_list))
  
# initializing i, j 
i, j = 4, 8
  
# list comprehension for 1 liner
res = [toggle(ele, i, j) for ele in test_list]
          
# printing result
print("The altered list : " + str(res))

输出：

The original list is : [4, 7, 8, 0, 8, 4, 2, 9, 4, 8, 4]
The altered list : [8, 7, 4, 0, 4, 8, 2, 9, 8, 4, 8]