Thank you guys, lots of great answers, very helpful. I got it!
A follow-up question:
How did the value of "object" get passed to "time"? Obviously, they have
different names. How did Python make that connection?
Code is below for convenience.
class Clock(object):
def __init__(self, time):
self.time = time
def print_time(self):
time = '6:30'
print(self.time)
clock = Clock('5:30')
clock.print_time()
5:30
Thank you!
On Thu, Mar 8, 2018 at 6:30 AM, Steven D'Aprano <
steve+comp.lang.pyt...@pearwood.info> wrote:
> 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
>
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