[0:00] hey everybody welcome back in this final
[0:02] part of my python project structure
[0:04] video series I'm going to look at
[0:06] extending the app we build just a little
[0:08] bit but using a general framework that
[0:11] you can use for all of your applications
[0:13] or scripts that you write in Python what
[0:15] we're going to be doing is adding a
[0:17] domain folder to group all of the domain
[0:20] Logic for our app uh Services folder
[0:23] which is going to have all of the sort
[0:25] of logic of our app and then an adapters
[0:27] folder which is going to include things
[0:29] that external to our app that we want to
[0:31] bring in and use in here this is a
[0:33] general purpose framework that you can
[0:35] use to structure your projects I got
[0:37] this idea from this architectures book
[0:39] for python the ideas discussed in this
[0:41] book apply to Big monolithic systems
[0:44] that are really complicated there's
[0:46] Advanced topics like a unit of work they
[0:49] have a lot of abstractions that make
[0:51] these really big systems work nicely so
[0:54] if this is so complicated and advanced
[0:55] why am I talking about it well there's a
[0:57] few basic ideas that I gleamed from here
[1:00] which I apply to my projects and
[1:02] basically just help me structure things
[1:05] so I've already talked about them in my
[1:06] own words but I'm going to use the
[1:08] author's words there's a domain layer
[1:10] this defines the business logic in our
[1:12] case with our example of a shopping cart
[1:15] with fruits in it the business logic is
[1:17] this concept of a fruit and a shopping
[1:20] cart these are our domain entities next
[1:22] we'll have a service later this defines
[1:24] the jobs the system should perform and
[1:26] orchestrates different components in our
[1:29] case we want want to add items to the
[1:31] shopping cart and remove them it's
[1:32] pretty much it so that's our service
[1:34] layer although the authors have more in
[1:36] here the last one that I use regularly
[1:39] is an adapter's layer concrete
[1:42] implementations of an interface that
[1:44] goes from our system to the outside
[1:46] world all right so the authors are
[1:49] describing this as a way of of of their
[1:52] system talking to the outside world this
[1:54] could be like a database integration
[1:56] where you want your system to write data
[1:58] to a database
[2:00] but for me I also use adapters to pull
[2:02] data in from the outside world so let's
[2:04] go ahead and restructure our project to
[2:07] work like this it's really easy first
[2:09] I'm going to hop into our shopping cart
[2:11] and make these folders that I've been
[2:12] describing I'll have one for domain
[2:15] Services adapters typing inside of each
[2:18] of these I'm going to put an init
[2:24] file and now the fruit file we just want
[2:27] to put this directly into adapters into
[2:29] here okay let's move my shopping cart
[2:31] now into Services let's check out fruit
[2:33] oops I accidentally put that in adapters
[2:36] okay that's in domain this is clearly
[2:38] like a domain entity and shopping cart
[2:41] is like a service right so I put that in
[2:42] here but I've got this domain object
[2:45] inside of here let's move that over
[2:48] shoppingcart
[2:50] py let's open that and paste and this is
[2:53] good because fruit is local now right to
[2:55] this domain so we we've got all our
[2:57] domain stuff together in one place and
[2:59] and now I I just want to make sure we
[3:01] get rid of it here get rid of that
[3:03] probably don't need data classes now I
[3:05] don't have my shopping cart I'm going to
[3:07] go to my domain shopping import shopping
[3:11] cart so here's my project so if I run my
[3:14] app so it's not finding a module named
[3:17] shopping cart. shopping cart anymore and
[3:20] maybe this is my init files I never
[3:22] updated that so let's go back in this
[3:25] init file I'm grabbing some stuff from
[3:27] shopping cart now in my services like so
[3:30] I have to update that and for fruit
[3:33] that's in my domain now see let's try it
[3:34] again fruit is not defined I suppose
[3:37] what I did do inside of my shopping cart
[3:40] service I probably have a fruit object
[3:44] here just instead of shopping cart I
[3:49] want fruit right and uh I'll do it this
[3:54] way just grab it like that still feeling
[3:56] pretty good U I'm not really going to
[3:57] think too much about it let's try and
[3:59] run it again great it worked so my app
[4:01] is still working after refactoring it
[4:04] well let's throw together a quick
[4:05] example on the Fly of how we might want
[4:07] to have an adapter for this application
[4:10] let's imagine we're like an e-commerce
[4:11] website where users will have a shopping
[4:13] cart what you might want to do is
[4:15] classify those users for like a
[4:17] propensity of how valuable they are
[4:19] maybe all the items in the shopping cart
[4:21] are worth like a lot of money so we
[4:22] should kind of identify that let me go
[4:24] ahead and build this starting in the
[4:26] services layer score shopping cart and
[4:30] let's add some documentation assign a
[4:33] score to the shopping cart based on the
[4:39] contents like the other functions here
[4:42] we want to add a shopping cart we're
[4:45] passing in like what our current cart is
[4:47] now what I want to do is score it here's
[4:49] where our adapters layer is going to
[4:51] come in so I'll say from adapters score
[4:55] and I'm going to say import shopping
[4:57] card scorer so no I'm using camel case
[5:02] or rather like python convention for an
[5:04] object goe and initialize it in here
[5:06] score do score and I'm going to pass in
[5:10] my cart this will provide me score I'll
[5:12] call it cart
[5:14] score I'm going to assign this to the
[5:16] shoing cart object let's remind oursel
[5:19] of what that looks like so now I could
[5:20] have a score down here and I'm going to
[5:22] call that int it's going to be an
[5:23] integer score and it's going to default
[5:25] To None because we don't need to have a
[5:28] score when we're initializing shopping
[5:30] cart let's go back to our services cart
[5:33] doore equals
[5:35] this assigning score cart
[5:40] score okay so what do we have to do now
[5:42] well this shopping cart score doesn't
[5:44] exist we need to create it and we need
[5:46] to make sure that it has this right
[5:47] method I'm going to create a score file
[5:51] and we know we need these things so
[5:52] class shoing card scorer is going to
[5:55] come in here and this is going to have
[5:57] to do some stuff let is going to have to
[5:59] to have this
[6:03] method okay it's going to pick itself
[6:06] and a cart when we initialize
[6:08] this I'm not going to actually do
[6:10] anything when we initialize this and
[6:12] then for this guy here um we need to
[6:15] make sure he's returning an integer I
[6:17] could just say that score is going to
[6:19] equal and I could say item. price for
[6:24] item in cart.
[6:27] items and I could say or zero because
[6:32] the price might be none and then I can
[6:34] just sum those up and I could return
[6:37] that as a score one last thing I want to
[6:40] do is pass that as an integer or I guess
[6:43] to this would be more in line with the
[6:46] Zen of python to do things this way
[6:48] pretty happy with with everything here
[6:50] even though I'm not really using my
[6:51] initialization method in general I might
[6:53] want to do that now one other thing I
[6:55] might want to do here is say from domain
[6:59] do shopping cart import go here and
[7:04] explicitly say what we're passing in
[7:07] here um let's see if everything uh works
[7:09] if I run my app that seems to be working
[7:11] the thing is my app's not actually doing
[7:14] anything we're going to need to import
[7:16] that so if I go back to my services here
[7:19] it is score shopping cart is what I want
[7:22] put that here okay so I'm just going to
[7:26] import it along with everything else and
[7:28] then if I go to the again and grab the
[7:30] names now where am I doing okay so now I
[7:33] want to score this and I want to score
[7:35] my card and that was it I didn't have
[7:36] any other arguments so after I do that
[7:38] if I print my cart
[7:40] again and I'll just say
[7:43] print and we'll be able to see
[7:46] that see if it'll work it can't import
[7:49] that I believe it's because I didn't add
[7:51] it to my
[7:53] init okay so score shopping cart cool
[7:57] let's see so here it's assigning a score
[7:59] zero because um I have no prices when I
[8:01] add my fruits I'll just assign some
[8:04] arbitrary prices say $99 because these
[8:07] are the most fantastic fruits in the
[8:09] world and there's my score of 198 you
[8:11] could stop watching here and I wouldn't
[8:13] blame you and if you do I thank you for
[8:16] going this far with me I would really
[8:18] appreciate it if you consider giving
[8:20] these videos a like or maybe subscribing
[8:22] to my channel if you like this content
[8:24] as a new channel this really helps me
[8:27] get visibility if you liked my layout
[8:29] with the terminal I have another video
[8:32] on using vim and t-o and how I've
[8:35] configured these things it will send
[8:37] your productivity into an absolute
[8:39] spiraling death I mean um I mean uh you
[8:43] should check that out a little bonus the
[8:45] last thing I'm going to do is make this
[8:47] adapter better we might want to have
[8:49] different ways of scoring things what
[8:51] I've created here is more of like a base
[8:54] score it's almost more like a unit test
[8:56] really I make a new folder and I'm going
[8:58] to call it Gore
[9:00] plural and then inside of here I'm going
[9:02] to I'm going to copy this guy and I'm
[9:04] going to put it in here delete I want to
[9:06] call this a base score rename it and I'm
[9:08] going to rename it base I guess py
[9:11] called this base shopping cart score I'm
[9:14] going to have to go down an additional
[9:16] level so I'll add another dot there
[9:18] where am I going with this well I might
[9:20] want to have different scores I'm going
[9:21] to copy this guy and I'm going to paste
[9:22] it what do we want to call another score
[9:25] Apex I don't know what that means but
[9:27] let's say we have some model we've
[9:29] called it Apex okay so let's call that
[9:31] Apex shopping cart score so I could
[9:34] imagine one situation where I have a
[9:37] different projects set up for this Apex
[9:39] and I can say from Apex scorer import
[9:43] shopping cart
[9:46] score and then I could go down here and
[9:49] where I have score shopping cart I just
[9:52] want to return the Apex call to shopping
[9:57] 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