Python Memory Management and Tips Transcripts
Chapter: Memory and classes
Lecture: Plain ol' fields

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0:00 Alright, let's jump back in and just start writing some code. Go back to our project we're working on,
0:06 and we're gonna add another app, this is gonna be "app_props_and_classes". We'll give that the fmain magic and set it up to
0:14 run. Alright, So I would like to be able to create a class. We're going to keep working with this person idea,
0:23 that applies to all of them, but we're just gonna keep rolling with this idea of a person. But I would like you to write a class that,
0:29 given that class, it's going to behave like this. We'll be able to come over here and have a datetime, which is the birthday. A monthly income,
0:39 which is a number, and we'll create a person, Sarah Sampson, given the birthday and the monthly income, and then it will have her full name,
0:46 which will be Sarah Sampson, Like that, from her two name parts. How old she is in years based on right now,
0:53 her yearly income, how long until she retires and so on. So we're gonna do this three different times.
1:00 The first one we're going to create what I'll call the "naive person object",
1:04 and that is just write this in the most straightforward way that you would with Python classes. And then we're gonna make one improvement and another.
1:12 So, I'm gonna create a little place to store those three classes over here. I'll call this "props_people". I wouldn't normally organize this,
1:21 I'd just call it person or something. We've already got several persons rolling around. And we're gonna have a naive, let's say
1:28 "PersonNaive" like this, and let's just remind ourselves what that was that we're going after.
1:37 We'll come over here and we'll create an initializer, a constructor, and it's gonna have to take first name, last name, birthdate and monthly income.
1:53 Those are the things that are passing in. This one's gonna be an integer. This will be a datetime, datetime, like so, and strings and strings.
2:10 Then let's just have PyCharm Add the fields to the class. So thank you pyCharm for doing that.
2:17 I do wish that it would not do it in reverse order that it would put them behind, not ahead. But you know,
2:23 So it goes. We can always reorder it. Like I feel like that should go up and those should probably go above, I don't know why.
2:31 So, so far that gets us down here. And now we're gonna have a full name and we'd like to be able to say
2:38 "object.full_name", so let's put that here. We'll say "self.full_name",
2:45 we'll just make an f-string, "self.first_name" we're not gonna need the "slef" at this point. First, last. Alright, that's gonna be the full name.
2:53 Ah, then we'll take care of this one. We need age in years. Well, what we need to know about age in years we're gonna need to hold on to
3:06 now. So we'll say "", call that function, and now is gonna be the time it is now. So, age in years, let's see,
3:17 we gotta go from their birthday over to this. So we'll say, I'll make an "age_delta" is gonna be now minus birthdate,
3:31 and this is gonna give us a time delta, which represents basically the seconds or the ticks. And there's a cool thing we could do with time
3:37 deltas, we can divide them, and I can come over here and say "days equals 365"
3:47 and that's gonna take however long that is and convert it to however many years. So over here we'll say, maybe we'll store it as an integer.
3:55 People think of themselves as having an integer age. You know, I'm not 36.271111 I'm you know, whatever, you know, 36. Or,
4:06 sometimes you round up a little early, but you talk about that in integers. So integers we're gonna put there. Yearly income, again.
4:14 This will be "self.yearly_income", that's 12 times the monthly income. That one was easy. And finally,
4:23 years until retirement. So "self.years_to_retire" is gonna be max of zero, because you might already be up for retirement, or "self.age_in_years",
4:35 let's say 65 minus that, because at least in the U.S., typically people retire at 65 on average. So, how long until you're 65 years old?
4:47 Alright, I think that this might do it. Let's go over here and we'll say "props_people import this one". Now, notice
5:00 This is a person. We're gonna have different variations. So here's the thing that is not normally done in programming, but I'm going to do here.
5:06 I'm gonna come over and redefine, have a person type, which is gonna be a person_naive at first.
5:16 And then we'll have a global person type, nut we can change this to affect other functions. So in the beginning, we're going to start with this.
5:23 We could even say testing, or, "running with person implementation: {person.__name__}" if this was and f-string, like that.
5:37 And then what we want to do is we just want to run "retirement_summary()" right? That's a lot of work, but it set the stage for this exploration.
5:47 Maybe I'll spell this correctly rather than PyCharm spell it correctly. Let's go ahead and run and see what happened. Yes! It works! so hi
5:56 Sarah Sampson, let's review your retirement. Your 46 years old. You currently make $84,000 USD a year.
6:03 You have 19 until retirement. Maybe units belong there. I'll be sure to put some bank, some money in the bank and retire for retirement
6:10 each month. Um, there you go, 19 years, we're gonna say one years, but that's fine. I'm happy with that, it's okay. Good enough for our purpose here.
6:22 So this type of definition of this object here seems totally natural, right? It lets us go to our person, say person dot, we have age_in_years,
6:32 last, first, full_name, all the things that we want to work with and notice these are "f's" so these are fields
6:39 as opposed to functions or other types of things, this is great. What could go wrong? Well, it turns out it's not super efficient,
6:47 even if it is the most natural way to do things.

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