#100DaysOfCode in Python Transcripts
Chapter: Days 19-21: Iteration with itertools
Lecture: Itertools - Product
Login or
purchase this course
to watch this video and the rest of the course contents.
0:00
Let's take a quick look at itertools product.
0:03
Now product actually is short for Cartesian product
0:08
or it's a Cartesian product, I suppose.
0:11
Now, what does that mean?
0:12
Well, it's not another language.
0:13
It actually means it is every
0:16
possible combination of values.
0:20
Alright, so think of it this way.
0:21
Let's say you had a string.
0:23
Let's say you had my name
0:25
and you wanted to see how many different possible
0:29
combinations you could get of the letters.
0:33
Now you can change that slightly.
0:36
So, the first thing that comes to mind is that you
0:39
might think how many combinations of six letters.
0:43
So my name, J-U-L-I-A-N.
0:46
How many combinations of those six letters can you get?
0:52
Now with itertools product,
0:54
that is exactly what it calculates for you.
0:57
That's what it prints out on the screen for you.
1:00
So, let me demonstrate that for you.
1:01
Okay, so we've done from itertools import product.
1:05
For letter, and we'll use my name
1:07
just because we've discussed that.
1:09
For letter in product, now in product,
1:12
look at that tool tip, we choose the iterable,
1:14
the item that we're iterating over and the repeat.
1:18
Now the repeat, it's actually quite easy.
1:21
It's much easier to show it to you.
1:22
But the repeat is essentially how many of those letters
1:27
or those items in that iterable
1:30
you want to show up as a product.
1:33
Okay, so let me show you.
1:34
So, we're going to use my name.
1:38
Julian.
1:39
And then, for the repeat, we're going to say 1,
1:42
just like the tall tip.
1:43
And when we hit enter, or when we, sorry I should say
1:47
when we print out the letter.
1:51
You'll see we, because we repeat it only 1,
1:54
we're only saying, well we only want one group,
1:58
1 grouping, we're only going to use how many iterations
2:01
of this, how many combinations of this are we getting to
2:07
a maximum of 1 character or 1 object?
2:12
Okay, so you can see here
2:14
Julian, the J can only show up once.
2:17
Okay, because it's only repeated once.
2:19
So, if we change this, let's just copy this back out.
2:26
And we change this to 2,
2:29
we can go print, letter.
2:33
Now, watch what happens.
2:35
We get a lot more as a result.
2:37
Okay, so the first thing it does is it takes the letter J.
2:41
Well, we're repeating 2.
2:42
We're going to use a combination of 2 letters.
2:44
We want to maximum of 2, it can repeat twice, okay.
2:48
So, we're going to have J with J.
2:51
We're going to have J with U.
2:52
We're going to have J with L.
2:53
We're going to have J with I.
2:54
And so on through the list.
2:55
And once it exhausts, J being in the first position
3:00
and this other combination being in the second position
3:05
it then moves down to the U.
3:07
And then it repeats it all over again.
3:09
And then, L and so on.
3:11
And it keeps going.
3:13
Now one thing you'll notice,
3:16
is that we're talking about the positioning here.
3:18
Okay, so U and I appear together here.
3:23
But they also appear together here.
3:26
I and U.
3:28
The difference being obviously that because they're in a
3:30
different order, it counts as a different combination.
3:35
Remember, this is every possible combination.
3:38
While yes, they're still returned as U and I
3:42
you're still getting a U and an I returned,
3:44
because they're in a different order,
3:45
because they're in a
3:46
different technical combination, I suppose.
3:49
They are capable of showing up twice.
3:52
Okay, what you will also notice,
3:56
is that J, J, does not show up twice.
4:02
Okay, it shows up once, because it doesn't matter.
4:06
These aren't treated as different J's.
4:09
It is a J, plain and simple.
4:11
Okay, so it shows up J, J, just once.
4:16
And that is editor's product.
4:19
It's so simple, but just imagine trying to code this
4:25
yourself with a for loop
4:26
and looking at if statements and everything like that.
4:29
It's disgusting, right.
4:31
So, this is the power of itertools with just two lines of
4:34
code you can get every possible combination,
4:39
the Cartesian product of an iterable.
