Question

正如标题所述，编写以下代码的pythonic方法是什么？

if x == 1:
    myvar = "a string"
elif x == 2:
    myvar = "another string"
elif x == 3:
    myvar = "yet another string"
else:
    raise Exception("arg x must be 1, 2 or 3")

执行上述操作似乎有点笨拙，而对于更长的示例，则更加耗时且混乱。

Answer 1

您要为此使用字典：

x = 3 # Then try with 4

outcome_dict = {1: "some string", 2: "another string", 3: "yet another string"}

my_var = outcome_dict.get(x)

if my_var is None:
    raise Exception("arg x must be 1, 2 or 3")

print(my_var)

如果找不到密钥，则dict.get()方法将返回None。在此示例中，所有结果都需要在outcome_dict中手动键入，但实际上，很容易在单行代码中为数千个键：值对创建字典，例如字典理解或常规的for循环。

Answer 2

除了@roganjosh的解决方案之外，您还可以尝试使用try和except。

dict_values = {1: "some string", 2: "another string", 3: "yet another string"}

# Using for x = 3
x = 3

try:
    print (outcome_dict[x])
except:
    print ("arg x must be 1, 2 or 3")
# yet another string

# Using for x = 4
x = 4

try:
    print (outcome_dict[x])
except:
    print ("arg x must be 1, 2 or 3")
# arg x must be 1, 2 or 3

Python的方式来构造if语句来改变变量值？

2 个答案: