我应该使用类吗？ （蟒蛇） [英] Should I use a class? (Python)

问题描述

我想写一个小的Python模块，其中包含一些数学函数。例如，它可能包含如下的函数：

I'm trying to write a small Python module which contain some mathematical functions. For example, it might contain a function like:

def quad(x, a, b, c):
    return a*x**2 + b*x + c

除了变量 x 之外（ a，b，c 现在，如果我把它放在一个文件中，只是导入它，最终用户将不得不总是调用函数除了变量的参数。因为这样我想创建一个类如：

As you may notice it contains several parameters (viz. a, b, c) apart from the variable x. Now if I were to put this in a file and simply import it, the end user would have to always call the function with the parameters in addition to the variable. Because of this I was thinking of creating a class such as this:

class quad:                                    
    def __init__(self, a, b, c):               
        self.a = a                             
        self.b = b                             
        self.c = c                             

    def eq(x):                               
        return self.a*x**2 + self.b*x + self.c 

因此允许最终用户使用它作为：

Thus allowing the end user to use it as:

q = quad(p, q, r) 
eq = q.eq      

这是正确的做事方式吗？

Is this the right way of doing things? I am terribly sorry about the title of the question, as I couldn't think of a better one!

推荐答案

这看起来像是一个很好的问题，一个类的完美合理使用。基本上你应该考虑使用一个类，当你的程序涉及可以被建模为具有状态的对象的事物。这里，多项式的状态只是系数 a ， b 和 c

That seems like a perfectly reasonable use of a class. Essentially you should consider using a class when your program involves things that can be modelled as objects with state. Here, the "state" of your polynomial is just the coefficients a, b, and c.

您还可以使用Python的 __ call __ 特殊方法该类好像是一个函数本身：

You can also use Python's __call__ special method to allow you to treat the class as though it were a function itself:

class quad:
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

    def __call__(x):
        return self.a * x**2 + self.b * x + self.c

q = quad(p, q, r)
q(x)

---

还有一种方法可以稍微干净一点，函数，其中包含那些系数。这实际上是一个例子，如Tichodrama提到：

---

Yet another way of doing it, which could be slightly cleaner, would be simply to return a function with those coefficients baked into it. This is essentially an example of currying, as Tichodrama mentions:

def quad(a, b, c):
    def __quad(x):
        return a * x**2 + b * x + c

    return __quad

或使用 lambda 语法：

def quad(a, b, c):
    return lambda x: a * x**2 + b * x + c

这样可以这样使用：

q = quad(p, q, r)
q(x)

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