使用对象作为输入在python中定义方法

Question

I just started with coding in python, at the moment I am trying to define a function that needs an object as input. Before this I just developed in Java.

def welcome_message(c):
    msg.send("Hi %s", c.first_name)

So this function works, I was wondering if I still should insert a constraint that c has to be on object of the type Customer? It just doesn't really feel safe for a java experienced developer...

Answer 1

The python way of thinking is that the programmer or those that use your software will be intelligent enough to use it properly so long as you've written and documented your software clearly. More that likely when passing in the object, c.first_name will barf if it's not the right type. One way to protect things is the following:

def welcome_message(c):
    if isinstance(c, Customer):
        msg.send("Hi %s", c.first_name)
    else:
        raise TypeError("Class must be of type `Customer`")

However, I would recommend not doing this, unless it's absolutely necessary.

Answer 2

If an object without a first_name attribute is passed, this will fail. So put that function body in a try ... except and decide what you want to do when it fails.