Python Jumpstart by Building 10 Apps Transcripts
Chapter: App 7: Wizard Battle App
Lecture: Concept: Objects vs. Classes
0:00 Let's take a moment and focus on this concept of classes versus objects.
0:04 If you are new to object oriented programming and this idea of classes,
0:08 this can be a little bit tricky.
0:11 Recall, this is how we define a class,
0:13 we say class creature and it defines basically the blueprint.
0:17 Here is how we initialize it, and within that initialization here is the fields,
0:21 here is the other behaviors it has for example that it can walk around
0:25 and for creatures, there is only one creature class,
0:29 this is it, this is what a creature looks like in our program.
0:33 However, we can create many of these creatures,
0:36 here we are going to create a squirrel and its power,
0:40 you can see the parameter to the initialization method is power
0:43 so here we want to say creature (7),
0:46 we'recreating a squirrel with power 7 whatever that means
0:49 and then we are also creating a dragon which is more powerful, it has power 50,
0:53 so when we create the squirrel and the dragon,
0:56 these are objects, and objects are created via classes
1:00 but they each have their own pointer in memory
1:03 and that points to their own data.
1:06 So, this squirrel object it has its own power variable and its power is 7.
1:10 Now it actually gets the implementation from walk, from the blueprint,
1:15 but we can call walk on this squirrel and we'll work with its data,
1:19 its power of 7 and so on,
1:20 the dragon has another pointer,
1:23 somewhere else in the memory and it has its own copy of power,
1:26 so if we change the dragon's power
1:29 obviously it's unrelated to the creature so these are objects,
1:31 they are created from the class, from the blueprint of what defines a creature,
1:35 and then we can call squirrel that walk dragon that walk
1:39 and they may have different behavior based on the power,
1:41 maybe if there is a lot of power it jumps around
1:44 if it doesn't have much it sort of scurries or something like this.
1:47 Once you get used to this idea of classes and objects
1:50 it's really straightforward and you'll have it down no problem,
1:53 but if this is new to you, make sure that you get this idea,
1:55 it's the core concept in object oriented programming
1:59 classes, inheritance in object oriented programming
2:01 play a really central role in Python.