Python - 更改列表中元组元素的符号

给定一个双元组列表，任务是编写一个Python程序，将第二个元素转换为每个元组的负值，将第一个元素转换为每个元组的正值。

Input : test_list = [(3, -1), (-4, -3), (1, 3), (-2, 5), (-4, 2), (-9, -3)]

Output : [(3, -1), (4, -3), (1, -3), (2, -5), (4, -2), (9, -3)]

Explanation : All the first elements are positive, and 2nd index elements are negative, as desired.

Input : test_list = [(3, -1), (-4, -3), (1, 3), (-2, 5)]

Output : [(3, -1), (4, -3), (1, -3), (2, -5)]

Explanation : All the first elements are positive, and 2nd index elements are negative, as desired.

方法 1：使用循环和abs()

在这种情况下，我们使用循环进行迭代，并使用 abs() 最初将两者转换为正数。第二个元素带有符号“-”，并根据需要转换为负元素。

例子：

Python3

# initializing lists
test_list = [(3, -1), (-4, -3), (1, 3), (-2, 5), (-4, 2), (-9, -3)]
  
# printing original list
print("The original list is : " + str(test_list))
  
res = []
for sub in test_list:
  
    # 2nd element converted to negative magnitude
    res.append((abs(sub[0]), -abs(sub[1])))
  
# printing result
print("Updated Tuple list : " + str(res))

输出：

The original list is : [(3, -1), (-4, -3), (1, 3), (-2, 5), (-4, 2), (-9, -3)]

Updated Tuple list : [(3, -1), (4, -3), (1, -3), (2, -5), (4, -2), (9, -3)]

方法 2：使用列表理解 

与上述方法类似，唯一的区别是使用列表理解作为一个 liner 来执行此任务。

例子：

蟒蛇3

# initializing lists
test_list = [(3, -1), (-4, -3), (1, 3), (-2, 5), (-4, 2), (-9, -3)]
  
# printing original list
print("The original list is : " + str(test_list))
  
# list comprehension used as one liner
res = [(abs(sub[0]), -abs(sub[1])) for sub in test_list]
  
# printing result
print("Updated Tuple list : " + str(res))

输出：

The original list is : [(3, -1), (-4, -3), (1, 3), (-2, 5), (-4, 2), (-9, -3)]

Updated Tuple list : [(3, -1), (4, -3), (1, -3), (2, -5), (4, -2), (9, -3)]