General Architecture Framework for a Python App

[00:00] hey everybody welcome back in this final

[00:02] part of my python project structure

[00:04] video series I'm going to look at

[00:06] extending the app we build just a little

[00:08] bit but using a general framework that

[00:11] you can use for all of your applications

[00:13] or scripts that you write in Python what

[00:15] we're going to be doing is adding a

[00:17] domain folder to group all of the domain

[00:20] Logic for our app uh Services folder

[00:23] which is going to have all of the sort

[00:25] of logic of our app and then an adapters

[00:27] folder which is going to include things

[00:29] that external to our app that we want to

[00:31] bring in and use in here this is a

[00:33] general purpose framework that you can

[00:35] use to structure your projects I got

[00:37] this idea from this architectures book

[00:39] for python the ideas discussed in this

[00:41] book apply to Big monolithic systems

[00:44] that are really complicated there's

[00:46] Advanced topics like a unit of work they

[00:49] have a lot of abstractions that make

[00:51] these really big systems work nicely so

[00:54] if this is so complicated and advanced

[00:55] why am I talking about it well there's a

[00:57] few basic ideas that I gleamed from here

[01:00] which I apply to my projects and

[01:02] basically just help me structure things

[01:05] so I've already talked about them in my

[01:06] own words but I'm going to use the

[01:08] author's words there's a domain layer

[01:10] this defines the business logic in our

[01:12] case with our example of a shopping cart

[01:15] with fruits in it the business logic is

[01:17] this concept of a fruit and a shopping

[01:20] cart these are our domain entities next

[01:22] we'll have a service later this defines

[01:24] the jobs the system should perform and

[01:26] orchestrates different components in our

[01:29] case we want want to add items to the

[01:31] shopping cart and remove them it's

[01:32] pretty much it so that's our service

[01:34] layer although the authors have more in

[01:36] here the last one that I use regularly

[01:39] is an adapter's layer concrete

[01:42] implementations of an interface that

[01:44] goes from our system to the outside

[01:46] world all right so the authors are

[01:49] describing this as a way of of of their

[01:52] system talking to the outside world this

[01:54] could be like a database integration

[01:56] where you want your system to write data

[01:58] to a database

[02:00] but for me I also use adapters to pull

[02:02] data in from the outside world so let's

[02:04] go ahead and restructure our project to

[02:07] work like this it's really easy first

[02:09] I'm going to hop into our shopping cart

[02:11] and make these folders that I've been

[02:12] describing I'll have one for domain

[02:15] Services adapters typing inside of each

[02:18] of these I'm going to put an init

[02:24] file and now the fruit file we just want

[02:27] to put this directly into adapters into

[02:29] here okay let's move my shopping cart

[02:31] now into Services let's check out fruit

[02:33] oops I accidentally put that in adapters

[02:36] okay that's in domain this is clearly

[02:38] like a domain entity and shopping cart

[02:41] is like a service right so I put that in

[02:42] here but I've got this domain object

[02:45] inside of here let's move that over

[02:48] shoppingcart

[02:50] py let's open that and paste and this is

[02:53] good because fruit is local now right to

[02:55] this domain so we we've got all our

[02:57] domain stuff together in one place and

[02:59] and now I I just want to make sure we

[03:01] get rid of it here get rid of that

[03:03] probably don't need data classes now I

[03:05] don't have my shopping cart I'm going to

[03:07] go to my domain shopping import shopping

[03:11] cart so here's my project so if I run my

[03:14] app so it's not finding a module named

[03:17] shopping cart. shopping cart anymore and

[03:20] maybe this is my init files I never

[03:22] updated that so let's go back in this

[03:25] init file I'm grabbing some stuff from

[03:27] shopping cart now in my services like so

[03:30] I have to update that and for fruit

[03:33] that's in my domain now see let's try it

[03:34] again fruit is not defined I suppose

[03:37] what I did do inside of my shopping cart

[03:40] service I probably have a fruit object

[03:44] here just instead of shopping cart I

[03:49] want fruit right and uh I'll do it this

[03:54] way just grab it like that still feeling

[03:56] pretty good U I'm not really going to

[03:57] think too much about it let's try and

[03:59] run it again great it worked so my app

[04:01] is still working after refactoring it

[04:04] well let's throw together a quick

[04:05] example on the Fly of how we might want

[04:07] to have an adapter for this application

[04:10] let's imagine we're like an e-commerce

[04:11] website where users will have a shopping

[04:13] cart what you might want to do is

[04:15] classify those users for like a

[04:17] propensity of how valuable they are

[04:19] maybe all the items in the shopping cart

[04:21] are worth like a lot of money so we

[04:22] should kind of identify that let me go

[04:24] ahead and build this starting in the

[04:26] services layer score shopping cart and

[04:30] let's add some documentation assign a

[04:33] score to the shopping cart based on the

[04:39] contents like the other functions here

[04:42] we want to add a shopping cart we're

[04:45] passing in like what our current cart is

[04:47] now what I want to do is score it here's

[04:49] where our adapters layer is going to

[04:51] come in so I'll say from adapters score

[04:55] and I'm going to say import shopping

[04:57] card scorer so no I'm using camel case

[05:02] or rather like python convention for an

[05:04] object goe and initialize it in here

[05:06] score do score and I'm going to pass in

[05:10] my cart this will provide me score I'll

[05:12] call it cart

[05:14] score I'm going to assign this to the

[05:16] shoing cart object let's remind oursel

[05:19] of what that looks like so now I could

[05:20] have a score down here and I'm going to

[05:22] call that int it's going to be an

[05:23] integer score and it's going to default

[05:25] To None because we don't need to have a

[05:28] score when we're initializing shopping

[05:30] cart let's go back to our services cart

[05:33] doore equals

[05:35] this assigning score cart

[05:40] score okay so what do we have to do now

[05:42] well this shopping cart score doesn't

[05:44] exist we need to create it and we need

[05:46] to make sure that it has this right

[05:47] method I'm going to create a score file

[05:51] and we know we need these things so

[05:52] class shoing card scorer is going to

[05:55] come in here and this is going to have

[05:57] to do some stuff let is going to have to

[05:59] to have this

[06:03] method okay it's going to pick itself

[06:06] and a cart when we initialize

[06:08] this I'm not going to actually do

[06:10] anything when we initialize this and

[06:12] then for this guy here um we need to

[06:15] make sure he's returning an integer I

[06:17] could just say that score is going to

[06:19] equal and I could say item. price for

[06:24] item in cart.

[06:27] items and I could say or zero because

[06:32] the price might be none and then I can

[06:34] just sum those up and I could return

[06:37] that as a score one last thing I want to

[06:40] do is pass that as an integer or I guess

[06:43] to this would be more in line with the

[06:46] Zen of python to do things this way

[06:48] pretty happy with with everything here

[06:50] even though I'm not really using my

[06:51] initialization method in general I might

[06:53] want to do that now one other thing I

[06:55] might want to do here is say from domain

[06:59] do shopping cart import go here and

[07:04] explicitly say what we're passing in

[07:07] here um let's see if everything uh works

[07:09] if I run my app that seems to be working

[07:11] the thing is my app's not actually doing

[07:14] anything we're going to need to import

[07:16] that so if I go back to my services here

[07:19] it is score shopping cart is what I want

[07:22] put that here okay so I'm just going to

[07:26] import it along with everything else and

[07:28] then if I go to the again and grab the

[07:30] names now where am I doing okay so now I

[07:33] want to score this and I want to score

[07:35] my card and that was it I didn't have

[07:36] any other arguments so after I do that

[07:38] if I print my cart

[07:40] again and I'll just say

[07:43] print and we'll be able to see

[07:46] that see if it'll work it can't import

[07:49] that I believe it's because I didn't add

[07:51] it to my

[07:53] init okay so score shopping cart cool

[07:57] let's see so here it's assigning a score

[07:59] zero because um I have no prices when I

[08:01] add my fruits I'll just assign some

[08:04] arbitrary prices say $99 because these

[08:07] are the most fantastic fruits in the

[08:09] world and there's my score of 198 you

[08:11] could stop watching here and I wouldn't

[08:13] blame you and if you do I thank you for

[08:16] going this far with me I would really

[08:18] appreciate it if you consider giving

[08:20] these videos a like or maybe subscribing

[08:22] to my channel if you like this content

[08:24] as a new channel this really helps me

[08:27] get visibility if you liked my layout

[08:29] with the terminal I have another video

[08:32] on using vim and t-o and how I've

[08:35] configured these things it will send

[08:37] your productivity into an absolute

[08:39] spiraling death I mean um I mean uh you

[08:43] should check that out a little bonus the

[08:45] last thing I'm going to do is make this

[08:47] adapter better we might want to have

[08:49] different ways of scoring things what

[08:51] I've created here is more of like a base

[08:54] score it's almost more like a unit test

[08:56] really I make a new folder and I'm going

[08:58] to call it Gore

[09:00] plural and then inside of here I'm going

[09:02] to I'm going to copy this guy and I'm

[09:04] going to put it in here delete I want to

[09:06] call this a base score rename it and I'm

[09:08] going to rename it base I guess py

[09:11] called this base shopping cart score I'm

[09:14] going to have to go down an additional

[09:16] level so I'll add another dot there

[09:18] where am I going with this well I might

[09:20] want to have different scores I'm going

[09:21] to copy this guy and I'm going to paste

[09:22] it what do we want to call another score

[09:25] Apex I don't know what that means but

[09:27] let's say we have some model we've

[09:29] called it Apex okay so let's call that

[09:31] Apex shopping cart score so I could

[09:34] imagine one situation where I have a

[09:37] different projects set up for this Apex

[09:39] and I can say from Apex scorer import

[09:43] shopping cart

[09:46] score and then I could go down here and

[09:49] where I have score shopping cart I just

[09:52] want to return the Apex call to shopping

[09:57] cart score we're assuming that we have

[10:00] this somewhere else on our system and

[10:02] all we want to do is call that here and

[10:05] so this adapter lets us do that in a

[10:08] nice structured way so we have our Apex

[10:11] shopping card score object and we also

[10:14] have a base scoring object which does

[10:16] the same thing it has a scoring shopping

[10:18] cart function so these are implementing

[10:21] the same thing which is going to be

[10:23] important for what we do next so I'll

[10:25] have scorer. py so in here I'm going to

[10:27] create a new function score shop cing

[10:30] card I want a function that's going to

[10:31] bring in my objects from my subfolder in

[10:33] this case from do

[10:37] scores and then I'll do the same thing

[10:39] for

[10:40] base now in here I want a score type gu

[10:44] string I'm going to return a score a

[10:47] union of one of these so B basically it

[10:50] means it's one of these two things this

[10:52] is not really super clean I wouldn't

[10:54] actually want to do it this way but I'll

[10:56] say if the score type

[11:00] is equal to Apex bring that into our

[11:03] application and else if this is B like

[11:08] that okay good everybody's happy so I'm

[11:11] typing have Union if we haven't returned

[11:14] anything I'm going to raise a value

[11:16] error and a

[11:18] type and just a little exclamation mark

[11:21] and actually what I really want to do is

[11:23] I want to get the scar this is going to

[11:25] return an object and then I'm going to

[11:27] have to call that object still so by

[11:30] doing this the last thing I want to do

[11:33] is fetch that here and I can say in my

[11:35] init file for adapters I'll say from

[11:38] scorer I'll import um get scorer and uh

[11:43] let's go down and Implement that in our

[11:44] services now in my adapter's file I just

[11:48] put that in my init file is get score I

[11:52] can just fetch that directly out of my

[11:54] adapters now here is the shopping cart

[11:56] score no longer like that it's get score

[11:58] and I need a score type so score type

[12:01] and we're going to use um let's surface

[12:04] this type up to here and score type and

[12:09] it's going to be like a string we said

[12:11] so now that just kind of is going to get

[12:13] passed in from here

[12:18] oops okay happy with that and we're

[12:20] going to score our cart base on this

[12:23] score which is returned from here now we

[12:25] need to add the scor type to our app

[12:28] wherever I score my shopping cart here

[12:31] um I need my score type to be defined

[12:35] what I could do is make this a global

[12:36] variable in in my in my app here and I

[12:39] I'm going to say we're going to use the

[12:41] base one we know what to expect if I've

[12:43] done everything right this should just

[12:45] work okay it's saying no module named

[12:48] Apex scorer

[12:50] oh of course there's no module named

[12:52] Apex score because we just created that

[12:55] right it it it doesn't actually exist

[12:57] for the purposes of getting this working

[12:58] let's just like I don't know why I

[13:00] didn't see that coming leave that and

[13:03] say return zero and Implement score see

[13:07] if that does the trick uh score shopping

[13:10] cart is missing a cart argument okay

[13:14] yeah this is a weird one this is an

[13:16] object or this is a class you could call

[13:19] it score class just so you understand

[13:21] what's happening right and I need to

[13:22] initialize that I was not doing that

[13:25] that's what I want to do

[13:27] okay we're working here this is

[13:30] fantastic and one last thing I could do

[13:33] just for my own edification is in my app

[13:37] I want to try the other scor type our

[13:40] awesome Apex model which

[13:43] returns

[13:44] zero like we see here oh yeah okay this

[13:48] was a lot of fun as you can see it's got

[13:50] quite dark outside I have another video

[13:53] that talks about my t-u and my Vim

[13:55] config which has eaten up massive hours

[13:58] of my evenings this week and I think vim

[14:01] and t-o configs could eat up massive

[14:03] hours of your evening as well it has

[14:05] been fantastic to go through this demo

[14:08] and I hope you take these ideas and use

[14:10] them in your coding and build better

[14:12] python applications thanks so much and

[14:16] see you in the next one