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You have completed Python Type Hinting!
You have completed Python Type Hinting!
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The simplest type hinting is by using the built-in types. Let's see how to hint functions that are only concerned with the built-in types.
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I'm gonna to be using Python 3.6 and
PyCharm for all of these examples.
0:00
If you're still on Python 3.5, you'll
be able to follow along with everything
0:04
except where I do variable annotations.
0:07
That's a Python 3.6-only feature, but
that, along with some other additions and
0:10
fixes, are a great reason
to consider updating.
0:14
So let's start with a simple calculator.
0:17
So we've got add, subtract,
multiply, divide.
0:19
And we're just kind of being naive, and
0:22
we're just assuming whatever gets
passed in can be added together.
0:24
Like I said,
this is a really simple example.
0:27
So right now the calculator will work
with many different Python types, right?
0:30
We could add two strings together or
multiply a string by an integer.
0:33
We could, of course, do all of these
operations with ints, floats, or
0:36
other number types.
0:39
However, I want to optimize this code in
the future for use only with number type.
0:40
Now I could rename the functions,
0:45
but no one wants to type in add ints or
add numbers.
0:47
This is where type inting comes in handy,
0:51
especially since I know my team all
uses PyCharm for their development.
0:52
I don't need to import anything or
do anything special.
0:56
I can just annotate the functions right
where they are for simple cases like this.
0:59
So for instance,
on def add I can say that num1 is an int.
1:03
And I can say that num2 is an int.
1:07
And I can say that this
function returns an int, right?
1:10
Because int plus an int
always returns an int.
1:15
And I can leave the rest of this alone.
1:18
So I'm gonna go ahead and
add this to the others.
1:20
So int, int, and int.
1:22
Int, int, Returns an int.
1:32
And lastly, int int.
1:38
This doesn't return an int,
this would return a float, right?
1:43
Because dividing returns a float.
1:48
So we can already see that PyCharm is
alerting me to something being wrong here,
1:51
right?
1:56
Expected type 'int', got 'float' instead.
1:57
And here, Expected type 'int',
got 'string' instead.
2:00
So while these will still work, right?
2:03
Python will still run these, and
2:06
this will still be a perfectly
valid fine thing, right?
2:07
We can go here, and we can run calculator,
and we got 13.2 and
2:11
hello hello hello hello hello.
2:15
PyCharm was telling me that I didn't
use these in the way that I said I was
2:17
going to use them.
2:21
So that's pretty nice, right?
2:22
After each parameter, just to go
over this again, I add a colon and
2:24
the type that I expect
the parameter to be, right?
2:27
And at the end of the function definition,
I can include an arrow,
2:30
made by a hyphen and
a greater-than symbol, and
2:34
then the type that's going to
be returned by the function.
2:35
If I had a function that didn't return
anything, I could change this last word,
2:37
instead of float, to be None.
2:41
And Python knows that that function
now doesn't return anything.
2:43
And it's similar to a void
function in other languages.
2:46
Okay, so we've seen the error messages,
we've seen the things there, so, cool.
2:50
I need to get a little smarter in
my types that I'm using, right?
2:55
Because this right here is
perfectly valid for add.
2:59
I can add an int and a float together.
3:02
Now I could use a generic to say
that this can be an int or a float.
3:04
But, well, that's for the next video,
and there's an easier solution, anyway.
3:09
Python has a built-in type that's called
complex that can encompass both integers
3:14
and floats.
3:18
But also allows for
a third type of number, a complex number,
3:19
which is a combination of a real number
and an optional imaginary number.
3:22
So let me try changing
some of those to that.
3:26
So let's try changing this to complex,
3:28
and complex, and complex.
3:33
Cuz I don't know exactly
what's gonna come out of that.
3:37
And that gets rid of the error
message about the 5 and 8.2.
3:39
So okay, that's cool.
3:42
Now if I wanted to make sure that this
was only used for real numbers, though,
3:45
and not complex numbers, I can bring in,
from numbers important real.
3:50
I can bring in the real type, and the real
type is just encompassing ints and floats.
3:54
And again, I just say this is gonna
be a Real, and a Real, and a Real.
4:01
And I would do the same for
the rest of all of these functions.
4:06
My code is error-free, with the exception
of this 'hello Which I can't fix because I
4:10
can't have something that encompasses
numbers and strings this way.
4:14
So if you're dealing with simple types,
adding this kind of hinting right here is
4:17
remarkably simple and
gains you some decent benefits.
4:22
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