(Python) Return 来自 if 语句的值未分配给 if 语句外的变量

Question

def my_diet(event, style):
    if event == 1:
        choice = raw_input("""What type of animal are you?
        A) Carnivore
        B) Herbivore
        C) Omnivore
        """)
        if choice == "A":
            style = "Carnivore"
            print style
        elif choice == "B":
            style = "Herbivore"
        elif choice == "C":
            style = "Omnivore"
        else:
            style = "not-sure-yet"
        print style
    else:
        pass
    return style
    print style

eating_style = None
my_diet(1, eating_style)
print eating_style

控制台上打印的是：（假设choice = "A"）

食肉动物

None

这是否意味着 eating_style 是不可变的？如果是这样，我应该如何更改函数以将不同的值分配给 eating_style?

Answer 1

您的参数作为值传递。分配新值不会对其产生任何影响。你可以 return 像这样的新字符串。

def my_diet(event):
    if event == 1:
        choice = raw_input("""What type of animal are you?
        A) Carnivore
        B) Herbivore
        C) Omnivore
        """)
        style = ""
        if choice == "A":
            style = "Carnivore"
        elif choice == "B":
            style = "Herbivore"
        elif choice == "C":
            style = "Omnivore"
        else:
            style = "not-sure-yet"
    else:
        pass
    return style

eating_style = my_diet(1)
print eating_style

查看此 link 了解更多信息。 How do I pass a variable by reference?

(Python) Return 来自 if 语句的值未分配给 if 语句外的变量

(Python) Return value from if-statement does not get assigned to variable outside the if-statement

immutability

python-2.7