If you've programmed in other languages,

you've probably come across something called a switch.

A switch, is kinda like an IF conditional.

But it has multiple possibilities or cases as they're often called.

Python doesn't have switches.

And this is an intentional omission.

Switches, are often a source of bugs and can be really confusing for people.

We can, however, use a dictionary as a list of triggers and their actions.

Dictionaries though, as you remember, don't have an order.

No one wants a menu that keeps moving around them.

So, I'm gonna introduce you to a handy tool known as an ordered dict.

Every time we've built a menu so far, it's been, pretty simple, just one or

two choices that we've been presenting to the users,

as a string inside of the input function.

Well, I want this to be more like an application, as I've been talking about.

So, I wanna menu that looks more, professional.

Let's start by deciding our options.

So, what we're gonna do, is from collections, import OrderedDict.

And collections, if you haven't looked at it,

is a great part of the standard library that holds a lot of extra container types.

There are things like order to dict, and named tupple, which extend some built ins,

dictionaries and tupples, or there's like, whole new things, like counter, which

kinda looks and acts like a dictionary but doesn't work like a dictionary.

And way worth checking out.

Check all of it out, actually, whenever you get a chance.

We're gonna use ordered Dict, to keep the options in the order that we want.

So we can define our menu over one, let's just do it right up here.

So ordered Dict and so ordered Dict,

unlike regular dictionaries, remembers the order things are added.

The way it does this, is we add things as a list.

Which is kinda cool, in its own little way.

So, let's add our items.

Each one of our items,

is a tupple which actually a pretty common way of building a dictionary.

Play around with that, see if you can figure it out.

And what we're gonna do, is we're gonna use a letter.

So we're gonna say the letter A, is for add entry.

And we're gonna say the letter V is for, oops,

not quotes, is for view entry or entries.

So only two things in here, so far.

But, you know,

I'm pretty sure we're gonna add something else before the course is over.

The oder dic behaves just like a normal dictionary.

The only difference, as I said, is that it remembers the order that the keys went in.

They always come back out, in that same order.

So let's come down here to our menu loop function and let's use our menu.

Let's show the menu and handle whenever the user makes a choice.

All right so let's say choice is equal to none.

That's just you know, our way of setting a variable without giving it a value and

then let's say while choice, does not equal q let's

actually say while choice, yeah no that's fine.

So, while choice doesn't equal q.

We're gonna print out enter q to quit.

So we give them a nice, easy way of quitting.

So then, let's say for

key value, in menu.items, cuz remember, menu.items gives us a tuple.

We wanna get the key and the value.

We're gonna print, a string which has a placeholder.

And a parentheses, and another placeholder.

And we're gonna format that with the key, and value.dunder doc.

Talk about what that one is here in just a minute.

And then we're gonna say, choice, is equal to input.

That's the action and then lets lower case that and strip off any extra spaces.

Then lets do if choice in menu.

And then we're gonna do menu, choice.

All right, there's a lot going on here.

Let's break this down line by line.

So, first, like I said, we're setting our choice variable.

None is a pretty good and really,

really common way, of initializing a variable without giving it a value.

So, like in JavaScript, you know, you can do,

you know, var a, and suddenly you have a variable called a that has no value.

You can't do that in Python, so you set things equal to none.

Then, so long as they haven't chosen q as their choice, we're

gonna print out a message saying that hey you can put in q in order to quit.

Then, we're gonna loop through each of the items in our dictionary, the key and

the value and we're gonna print out the key and the value so

we'll get like A, and then something, that's where this value.dot comes in.

So what is value dot, doc?

Well, value is gonna be a function, right?

Because our keys, our functions, so add entry, sorry not our keys, our values.

Add entry is a value.

Add entry, is a function it's this function.

And this dunder doc is the doc string for that function.

So it's gonna say a, closing parentheses, add an entry.

That's kinda cool.

We're gonna capture their choice,

we're gonna let them type in whatever choice they want.

We're gonna lower case it and strip it.

We check to see if it's q, if it's q we're gonna quit.

If it's not q.

Then we come back to our menu,

we find the function that they've selected, and we run it.

I know there's a lot there, but it's all just laid out, one thing after the next.

Feel free to go in and add comments and, and all sorts of stuff here.

Just make sure you understand what's going on.

Let's give this a try, 'kay?

So we're gonna come back down here,./diary.

And if we look at this we get an error.

I said that it didn't matter where we put our menu, and it does matter.

So let's cut our menu out of there, and let's put our menu.

Right down here.

[BLANK_AUDIO]

All right.

Save that.

Sometimes these things happen.

There we go. There's our menu.

So it says enter q to quit, a to add an entry, v to view previous entries.

If I hit a.

It actually just comes right back, cause our function doesn't do anything.

I just hit 'V'.

Same thing.

Alright, I should be able to hit 'Q' in order to quit, and I quit.

Awesome.

We get a really nice looking menu.

I, I think it looks really nice.

We can choose our different actions.

They don't do anything right now, but we can choose them, and we can quit with 'Q'.

I think that's a great start.

So what do you think?

Is order dict a good way to deal with a menu?

I don't normally like using a dictionary as an alternate switch.

But I think they're a great idea in this use case.

It's clean, it's concise and it's easily extended.

Three of my favorite things.