Python for Absolute Beginners Transcripts
Chapter: The big ideas of software development
Lecture: Examples of code
Login or
purchase this course
to watch this video and the rest of the course contents.
0:00
Now let's look at a couple examples
0:02
of simple, software code that you're going to write
0:05
or could write, through this course.
0:07
What we have on the screen back here
0:09
is a little bit complicated but it's not too bad.
0:12
And you know how you feel about that, we're going to get there
0:15
but we're going to start much simpler than this.
0:17
The ideas we write in a very structured way
0:19
to tell the computer what to do.
0:21
So here, is a very simple Python program
0:24
or more accurately maybe a piece of a program.
0:27
It's what's called a function it says check_access
0:30
and it takes this thing called an age.
0:32
Now idea is, we should be able to use
0:34
this piece of functionality anywhere in our program
0:36
to ask the current user whose logged in
0:38
if we know their age, assuming that we do
0:41
we can ask are they allowed to create an account
0:43
are they allowed to access this part of our site
0:45
or whatever.
0:47
So right at the beginning of that purple line with hash
0:49
that is a comment, that's meant for us.
0:51
Much about writing software and computer code
0:54
really has to do with writing for humans
0:57
not writing for the machines.
0:59
Yes, of course, ultimately it's transformed for the machines
1:01
but humans have to understand it and maintain it
1:04
and it's read many more times than it's written
1:06
so we need to write it in a way that's super clear.
1:08
So we have this thing of a function
1:09
it's called check_access and given an age like 12
1:12
and it said no, no, no, no, we can't have anybody
1:14
who is 13 or younger, using our service.
1:17
So we can send out a little message, right
1:19
sorry you can't use this service
1:21
and we can tell whatever other part of the program
1:23
you did to use it, no, they're not allowed to do this.
1:26
In Python we say return False, so return the value
1:30
give back the value whoever asked
1:31
whether about you could use, this person can access
1:33
this part, tell them no and we don't have yes or no
1:36
we have true and false.
1:38
So if they're too young then we say, False.
1:40
But if we get past this check, if we're not true
1:43
that they're less than 14 they must be, 14 or older.
1:46
So then we can return true, yes anyone who is 14 or older
1:50
can use our service.
1:51
So, maybe you've not written a single line of Python yet
1:54
maybe you have, but possibly haven't, even so
1:57
spend a few moments with this
1:58
I think you could make sense of it.
2:00
That's one of the really cool things about Python
2:02
is it's actually pretty easy to understand.
2:05
Now they're very specific rules that we have to follow
2:07
alright it has to be if with a space
2:09
and then this test and then a colon
2:11
and then indented, for the code that it's going to
2:13
be within that case.
2:15
But once you learn the rules
2:16
it's actually not too hard at all.
2:19
Well, that was Python.
2:20
Notice, it's the same thing up here in the left.
2:22
Let's look at a couple of other languages
2:24
that has exactly the same behavior
2:27
and I think what you'll notice
2:28
is a lot of them have more symbol talk
2:31
or they're much more verbose.
2:33
They all accomplish exactly the same thing
2:36
but they're not necessarily as clear
2:38
or simple as Python.
2:39
Next one we have here in the middle, is C++.
2:43
This language is, one of the core languages that build
2:46
so many of the things that you use day to day.
2:49
Its been around since, I think the eighties
2:51
it's based on a language called C
2:52
which has been around even longer than that
2:54
and Windows was built with that.
2:57
A lot of video games was built with that
2:59
Linux was built with that
3:00
either C or C++
3:03
and this is one of the, low level languages
3:06
at least for software developers
3:07
not necessarily for computers
3:09
but you can see it does the same thing
3:10
and notice on this one we have to say what kind
3:13
of data is returned.
3:14
We have to say bool, check_access
3:16
and we also have to say what type of data
3:17
is accepted in integer.
3:19
Not a floating point number like 7.2
3:21
but seven, or eight.
3:24
And then of course this Boolean
3:25
is also a true and false
3:27
it's a very common idea.
3:28
Notice we have this if, basically the same test
3:31
but there's a lot more, curly braces
3:33
to indicate the ranges where parts running
3:36
the blocks have code, and then there's semicolons
3:38
to punctuate each line, C++.
3:41
This is common through many of the languages.
3:43
Over here we have visual basic.
3:45
Visual Basic is very very wordy
3:48
and Python is also kind of wordy doesn't have as many symbols
3:51
but for some reason
3:52
the Visual Basic words just get in the way
3:55
rather than clear things up
3:56
so here you could explicitly say we have a function
3:58
called check access
4:00
we're going to pass the age by value
4:01
which isn't integer
4:02
and then it's going to return a thing which is a Boolean.
4:05
Whoo, that's a lot to write.
4:07
But none the less it means the same thing
4:09
and we have another test.
4:10
If the age is less than 14
4:12
then we're going to tell you some other stuff.
4:14
Else, we're going to say, you know
4:16
check access is false or check access is true
4:18
the way you, return the indicated value
4:21
and Visual Basic is to set the value
4:23
of the thing you're running, the function.
4:25
We also have Javascript, this is very
4:27
one of the more popular languages.
4:29
It runs in your browser
4:30
it's the foundation of much of the interactive internet
4:32
at least on the browser side of things.
4:35
Here we're going to create a things that's var check_access
4:37
as a function that takes an age.
4:39
And again, from there on it's very very similar
4:42
to the C++ side of things
4:44
with curly braces, semicolons, and so on.
4:46
The way it actually runs is quite different.
4:48
And finally, we have C#
4:50
this is the .NET Microsoft language
4:52
along with VB as well.
4:54
And here we're going to have a program
4:56
and a thing called a class
4:58
and a public static function
5:00
there's a lot of descriptors in this
5:01
and the cases and scenarios which you can use them
5:04
but other than that once you get through all
5:06
this sort of wrapper stuff
5:07
then you end up with just like Javascript
5:09
just like C++
5:10
and do that test
5:12
curly braces to describe the blocks
5:14
semicolons to end the lines, and so on.
5:17
So, you can see a lot of commonalities
5:19
but also a lot of differences
5:21
amongst these different languages.
5:23
Python and VB are both more, word-driven
5:27
they don't have as many things
5:28
they don't have things like semicolons and curly braces
5:30
but VB still defines all its blocks
5:32
with like, closing type things like if and then
5:34
then and then, and if, and so on.
5:36
So, it's similar but also different
5:38
and then you can see the big influence
5:40
with the C++, Java Script, and C#, with there C heritage
5:44
curly braces, semicolons, and that sort of arrangement.
5:48
So here is the same program that
5:50
piece of program, piece of functionality
5:52
that we wrote before
5:53
in five different languages.
