处理班级中预设选项的最佳方法

Question

I want to have a Class which can be initialized with options a , b and c .

c is a special case, where I can modify the initialization with a variable extend .

I'm currently looking for the best way to do this. Also I would like my IDE (in this case PyCharm) to make suggestions to me which parameters I can use for the preset.

I came up with two ideas to do it.

Option 1:

class MyClass:
    def __init__(self,preset,extend=None):
        if preset == "a":
            self.x = 1
        if preset == "b":
            self.x = 2
        if preset == "c":
            self.x = 3
            if extend != None:
                self.x = self.x + extend
    def __str__(self):
        return f"The value of x is {self.x}"

Y=MyClass(preset="c",extend= 3)
print(Y)
#out: The value of x is 6

Option 2:

class MyClass2:
    def __init__(self):
        self.x=None
    def preset_a(self):
        self.x=1
    def preset_b(self):
        self.x=2
    def preset_c_with_extend(self,extend):
        self.x =3+extend

    def __str__(self):
        return f"The value of x is {self.x}"

Y2=MyClass2()
Y2.preset_b()
print(Y2)
#out: The value of x is 2

Option 1 looks more elegant to me, but in my workflow I don't want to go to the implementation for initializing a certain preset for looking up the options.

But this would be necessary, because I can not remember for bigger projects if I named the preset a or if it was not A . Option 1 also leaves it unclear if I can add an option extend . Here it might happen, that I use preset a with extend=3 and I am wondering why the extend is not applied.

So the actual question: Is there an elegant way to see the preset options without looking at the class implementation? (Maybe some kind of Type Hint?)

Option 2 has this opportunity, and with auto-completion in my IDE I see what presets I can apply. But it doesn't look very elegant.

I am curious about your ideas!

Answer 1

How about:

class MyClass2:
    def __init__(self, x):
        self.x = x
    @staticmethod
    def preset_a():
        return MyClass2(1)
    @staticmethod
    def preset_b():
        return MyClass2(2)
    @staticmethod
    def preset_c_with_extend(extend):
        return MyClass2(3+extend)

    def __str__(self):
        return f"The value of x is {self.x}"

Y2=MyClass2.preset_b()
print(Y2)

It ensures that x is set at object creation time and should allow IDE auto-completion.

Answer 2

Another alternative is to use a presets dict . However, I have no idea how PyCharm will treat this solution in regards to suggestions.

class MyClass:
    PRESETS = {"a": 1, "b": 2, "c": 3}

    def __init__(self, preset, extend=None):
        self.x = self.PRESETS.get(preset)

        if preset == "c" and extend is not None:
            self.x += extend

    def __str__(self):
        return f"The value of x is {self.x}"

Note that dict 's .get() method is used which means x will be None if you try to use a non-existing preset.