使用 class 内部的函数时出错。 我无法将 function 分配给新的 class 方法

Question

I'm trying to create a new method for my class 'Cloth', the method is called 'max_temp' and, to ease the task, i created the following function (max_temperature) to keep a cleaner code in the init part. I can't understand why it doesn't calculate the 'max_temp' method tho

class cloth():
    def __init__(self, category, name):
        self.category = category
        self.name = name
        self.max_temp = max_temperature(category)

    def max_temperature(category):
        temps = {
            'sweater' : 24,
            'shirt' : 45}
        return temps[category]

x = cloth('sweater', 'cam_eco')

print(x.max_temp)

>>> print(x.max_temp)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined

Answer 1

If you define a method inside a class then it needs to be either passed self as the first argument, or define it as a staticmethod or classmethod . Otherwise you need to define it outside the class.

So max_temperature needs to declared as one of:

@staticmethod # or @classmethod (Ill leave looking up the difference to you)
def max_temperature(category):
    ....

or

def max_temperature(self, category):
    ....

or define it outside the class.

If you define it inside the class then you should call it via self (or the class name if its a classmethod):

class cloth: # Note I removed the () from the class
    def __init__(self, category, name):
        self.category = category
        self.name = name
        self.max_temp = self.max_temperature(category)
...

So overall:

class cloth:
    def __init__(self, category, name):
        self.category = category
        self.name = name
        self.max_temp = self.max_temperature(category)

    @staticmethod
    def max_temperature(category): # TODO you should add error handling to this method
        temps = {
            'sweater' : 24,
            'shirt' : 45
        }
        return temps[category]

x = cloth('sweater', 'cam_eco')
print(x.max_temp) # 24

Answer 2

The question has been already answered by Austin, but If you are not ok with static concept yet, then your code will look like

    class cloth():
        def __init__(self, category, name):
            self.category = category
            self.name = name
            self.max_temp = self.max_temperature(category)

        def max_temperature(self,category):
            temps = {'sweater' : 24,'shirt' : 45}

            return temps[category]

    x = cloth('sweater', 'cam_eco')

    print(x.max_temp)

Answer 3

Have you tried using self.category as the argument in the max_temperature function?

class cloth():
    def __init__(self, category, name):
        self.category = category
        self.name = name
        self.max_temp = max_temperature(category)

    def max_temperature(self, self.category):
        temps = {
            'sweater' : 24,
            'shirt' : 45}
        return temps[category]

x = cloth('sweater', 'cam_eco')

print(x.max_temp)