On Saturday, September 2, 2017 at 6:34:59 PM UTC-4, Chris Roberts wrote: > Perhaps someone here could help me to get this into perspective. > Somehow when we start to feed an instance as the argument in a new instance. > my head explodes.. > in this case... > a = Foo() > b = Bar(a) > So... > a is a 'Foo instance' with properties and methods. > b is a 'Bar instance' > Since b is using the "a" instance as an argument?? > b=Bar(a) has what?? > > Is there an easier way to put into perspective how an instance of one class > is used as the argument into the instance of another class? > > Code below: > > class Foo(object): > bar = "Bar" # Class attribute. > > def __init__(self): > # #^ The first variable is the class instance in methods. > # # This is called "self" by convention, but could be any > name you want. > # ^ double underscore (dunder) methods are usually special. This one > # gets called immediately after a new instance is created. > > self.variable = "Foo" # instance attribute. > print self.variable, self.bar # <---self.bar references class > attribute > self.bar = " Bar is now Baz" # <---self.bar is now an instance > attribute > print self.variable, self.bar #variable will be a property of "a" and > self is the bound variable of a. > > def method(self, arg1, arg2): > # This method has arguments. You would call it like this: > instance.method(1, 2) > print "in method (args):", arg1, arg2 > print "in method (attributes):", self.variable, self.bar > > > a = Foo() # this calls __init__ (indirectly), output: > #a is Foo, a has a method called method, and properties such as "variable and > bar". > # Foo bar > # Foo Bar is now Baz > print a.variable # Foo > a.variable = "bar" > a.method(1, 2) # output: > # in method (args): 1 2 > # in method (attributes): bar Bar is now Baz > Foo.method(a, 1, > 2) # <--- Same as a.method(1, 2). This makes it a little more > explicit what the argument "self" actually is. > print "##Above is all the a Foo object, and below is the b Bar object" > > class Bar(object): > def __init__(self, arg): > self.arg = arg > self.Foo = Foo() #this calls and runs the Foo class again. > > > b = Bar(a) #b is a Bar object, a is a Foo object with properties and > methods. then Bar() calls the Foo class again. > b.arg.variable = "something" > print a.variable # something !(I don't know why "a" prints "something" here.) > print b.Foo.variable # Foo > > #### > OUTPUT: > Foo Bar > Foo Bar is now Baz > Foo > in method (args): 1 2 > in method (attributes): bar Bar is now Baz > in method (args): 1 2 > in method (attributes): bar Bar is now Baz > ##Above is all the a Foo object, and below is the b Bar object > Foo Bar > Foo Bar is now Baz > something > Foo > > #### Thanks in advance... crzzy1 ...
Steve and Irv, I see what you mean... I picked up on this example online and then tried to work it out on my own, but after seeing your replies, and looking further into cars examples I found how much more intuitive that makes it... Anyways, now I know where to better redirect my studies and energies. My work is sending me to a semi advanced (Core Python) class, and I am not ready, so trying to work on all my weak spots. Thanks -- https://mail.python.org/mailman/listinfo/python-list
