On Wed, 07 Mar 2018 16:57:51 -0500, C W wrote: > Hello, > > I am new to OOP. I'm a bit confused about the following code. > > class Clock(object): > def __init__(self, time): > self.time = time
Here you set the instance attribute "self.time". > def print_time(self): > time = '6:30' > print(self.time) Here you set the local variable "time", which is completely unrelated to the attribute "self.time". If you are used to languages where "foo" inside a method is a short-cut for "self.foo" or "this.foo", Python does not do that. Local variables and instance attributes are distinct concepts, and Python keeps them distinct. > How does line-by-line execution run inside a frame? There isn't actually line-by-line execution as such, although it can be very similar. Before the interpreter runs Python code, it compiles it to byte-code, and then runs the byte-code. A single line of source code could result in any number of lines of byte code, from zero to an unlimited number. > How does __init__ > work? I understand you must have __init__. You understand wrongly then :-) It is normal and common to have an __init__ method, but it is not compulsory. If your class doesn't need one, you don't need to write it. The __init__ method is the initialiser. Think of it as very similar to the constructor in some other languages, and for now the differences aren't important. The usual purpose of the __init__ method is to initialise the instance and set any attributes needed. > Is it run before print_time(), The __init__ method is called once, when the instance is first created. So the short answer is, yes, it will run before print_time(). But only once. > if so, why don't I just set self.time = '6:30' instead of > self.time = time? Because then every instance will be set to 6:30, instead of letting you set each instance to a different time. -- Steve -- https://mail.python.org/mailman/listinfo/python-list
