Python for Absolute Beginners Transcripts
Chapter: The big ideas of software development
Lecture: Examples of code
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Now let's look at a couple examples
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of simple, software code that you're going to write
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or could write, through this course.
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What we have on the screen back here
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is a little bit complicated but it's not too bad.
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And you know how you feel about that, we're going to get there
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but we're going to start much simpler than this.
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The ideas we write in a very structured way
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to tell the computer what to do.
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So here, is a very simple Python program
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or more accurately maybe a piece of a program.
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It's what's called a function it says check_access
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and it takes this thing called an age.
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Now idea is, we should be able to use
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this piece of functionality anywhere in our program
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to ask the current user whose logged in
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if we know their age, assuming that we do
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we can ask are they allowed to create an account
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are they allowed to access this part of our site
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or whatever.
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So right at the beginning of that purple line with hash
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that is a comment, that's meant for us.
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Much about writing software and computer code
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really has to do with writing for humans
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not writing for the machines.
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Yes, of course, ultimately it's transformed for the machines
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but humans have to understand it and maintain it
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and it's read many more times than it's written
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so we need to write it in a way that's super clear.
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So we have this thing of a function
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it's called check_access and given an age like 12
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and it said no, no, no, no, we can't have anybody
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who is 13 or younger, using our service.
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So we can send out a little message, right
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sorry you can't use this service
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and we can tell whatever other part of the program
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you did to use it, no, they're not allowed to do this.
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In Python we say return False, so return the value
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give back the value whoever asked
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whether about you could use, this person can access
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this part, tell them no and we don't have yes or no
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we have true and false.
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So if they're too young then we say, False.
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But if we get past this check, if we're not true
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that they're less than 14 they must be, 14 or older.
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So then we can return true, yes anyone who is 14 or older
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can use our service.
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So, maybe you've not written a single line of Python yet
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maybe you have, but possibly haven't, even so
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spend a few moments with this
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I think you could make sense of it.
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That's one of the really cool things about Python
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is it's actually pretty easy to understand.
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Now they're very specific rules that we have to follow
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alright it has to be if with a space
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and then this test and then a colon
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and then indented, for the code that it's going to
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be within that case.
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But once you learn the rules
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it's actually not too hard at all.
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Well, that was Python.
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Notice, it's the same thing up here in the left.
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Let's look at a couple of other languages
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that has exactly the same behavior
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and I think what you'll notice
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is a lot of them have more symbol talk
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or they're much more verbose.
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They all accomplish exactly the same thing
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but they're not necessarily as clear
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or simple as Python.
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Next one we have here in the middle, is C++.
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This language is, one of the core languages that build
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so many of the things that you use day to day.
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Its been around since, I think the eighties
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it's based on a language called C
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which has been around even longer than that
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and Windows was built with that.
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A lot of video games was built with that
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Linux was built with that
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either C or C++
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and this is one of the, low level languages
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at least for software developers
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not necessarily for computers
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but you can see it does the same thing
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and notice on this one we have to say what kind
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of data is returned.
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We have to say bool, check_access
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and we also have to say what type of data
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is accepted in integer.
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Not a floating point number like 7.2
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but seven, or eight.
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And then of course this Boolean
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is also a true and false
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it's a very common idea.
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Notice we have this if, basically the same test
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but there's a lot more, curly braces
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to indicate the ranges where parts running
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the blocks have code, and then there's semicolons
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to punctuate each line, C++.
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This is common through many of the languages.
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Over here we have visual basic.
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Visual Basic is very very wordy
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and Python is also kind of wordy doesn't have as many symbols
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but for some reason
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the Visual Basic words just get in the way
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rather than clear things up
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so here you could explicitly say we have a function
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called check access
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we're going to pass the age by value
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which isn't integer
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and then it's going to return a thing which is a Boolean.
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Whoo, that's a lot to write.
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But none the less it means the same thing
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and we have another test.
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If the age is less than 14
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then we're going to tell you some other stuff.
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Else, we're going to say, you know
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check access is false or check access is true
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the way you, return the indicated value
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and Visual Basic is to set the value
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of the thing you're running, the function.
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We also have Javascript, this is very
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one of the more popular languages.
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It runs in your browser
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it's the foundation of much of the interactive internet
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at least on the browser side of things.
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Here we're going to create a things that's var check_access
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as a function that takes an age.
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And again, from there on it's very very similar
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to the C++ side of things
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with curly braces, semicolons, and so on.
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The way it actually runs is quite different.
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And finally, we have C#
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this is the .NET Microsoft language
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along with VB as well.
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And here we're going to have a program
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and a thing called a class
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and a public static function
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there's a lot of descriptors in this
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and the cases and scenarios which you can use them
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but other than that once you get through all
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this sort of wrapper stuff
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then you end up with just like Javascript
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just like C++
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and do that test
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curly braces to describe the blocks
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semicolons to end the lines, and so on.
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So, you can see a lot of commonalities
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but also a lot of differences
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amongst these different languages.
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Python and VB are both more, word-driven
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they don't have as many things
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they don't have things like semicolons and curly braces
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but VB still defines all its blocks
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with like, closing type things like if and then
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then and then, and if, and so on.
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So, it's similar but also different
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and then you can see the big influence
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with the C++, Java Script, and C#, with there C heritage
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curly braces, semicolons, and that sort of arrangement.
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So here is the same program that
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piece of program, piece of functionality
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that we wrote before
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in five different languages.