如何在 Python 中使用 if-else 语句在多个变量之间切换

Question

如何使用单个开关变量在多个变量之间进行切换？

更新：澄清意图是无限次地在这两组变量之间切换。

当我尝试这个时，我收到以下错误。

a1= 'process1'
a2 = 'process2'

b1 = 'action1'
b2 = 'action2'

switch = True # the switch to indicate which set of variables to use
N = 10        # the number of times to switch between the two sets of variables

# alternate between two sets of variables N times
for i in range (N):
    active_process, active_action = a1, b1 if switch else a2, b2

    print("active_process: %s, active_action is: %s" %(active_process, active_action))
    switch = not switch

追溯：

Traceback (most recent call last):
  File "/home/username/.PyCharm2019.3/config/scratches/scratch_10.py", line 10, in <module>
    active_process, active_action = a1, b1 if switch else a2, b2
ValueError: too many values to unpack (expected 2)

Process finished with exit code 1

Answer 1

你让这太脆弱了。 您有一个问候/响应值表和一个告诉您使用哪个值的布尔值。 只需使用直接访问列表执行此操作：

table = [ ("process1", "action1"),
          ("process2" , "action2")
        ]

N = 10
for i in range(10):
    print("%s, the answer is: %s" % table[i %2])

或者，使用字典：

table = { True:  ("process1", "action1"),
          False: ("process2" , "action2")
        }
N = 10
for i in range(N):
    print("%s, the answer is: %s" % table[i %2])

Answer 2

使用列表打包和解包项目给出了预期的结果：

a1= 'process1'
a2 = 'process2'

b1 = 'action1'
b2 = 'action2'

switch = True # the switch to indicate which set of variables to use
N = 10        # the number of times to switch between the two sets of 

# alternate between two sets of variables N times
for i in range (N):
    [active_process, active_action] = [a1, b1] if switch else [a2, b2]

    print("active_process: %s, active_action is: %s" %(active_process, active_action))
    switch = not switch

输出：

active_process: process1, active_action is: action1
active_process: process2, active_action is: action2
active_process: process1, active_action is: action1
active_process: process2, active_action is: action2
active_process: process1, active_action is: action1
active_process: process2, active_action is: action2
active_process: process1, active_action is: action1
active_process: process2, active_action is: action2
active_process: process1, active_action is: action1
active_process: process2, active_action is: action2

Process finished with exit code 0