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Instructor: It's time to talk

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about another topic that sounds a lot more confusing,

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short circuiting than it actually is.

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It's quite simple.

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Short circuiting looks something like this.

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Remember when I taught you the word and

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so we can use...

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let's say for example, is friend equals to true.

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And let's say is user is equal to true.

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And I can do an expression here

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saying is friend and is user.

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Now in here when we run this

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let's print it here just so we can see.

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If I run this I get true

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because both of these evaluate to true.

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So that if I had this as an if block,

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let's say if it was if is friend and is user.

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Print best friends forever.

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Now short circuiting can be done when we use

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something like or, which we haven't seen before.

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But again, you can see here that it's highlighted in blue.

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So it is a keyword, a Python keyword.

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Now or says if either one of these conditions are true

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then run this piece of code.

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So if I run this, I get best friends forever.

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Now let me ask you this.

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Which operation do you think is more performant?

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The or or the end?

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Is there a difference?

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As a matter of fact, there is because of short circuiting.

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You see when I do or here,

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because I only care if either one of these is true.

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The Python interpreter is going to say

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if is friend and it's going to evaluate that

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and say, oh, this is, this is true.

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And then it's going to see the word or

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and it's going to say, hey, I don't care what this is.

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Maybe this is a really heavy operation

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or something that I need to look up.

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Well I don't really care because this is already true.

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Whether this is true or this is false, I don't really care

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because either way I'm going to have to print this.

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As you can see, it still prints best friends forever.

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So short circuiting happens when the interpreter

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is smart enough to say, I already did enough work.

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I don't care what this is,

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this is just wasted work if I do it.

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So I'm going to short circuit and say, hey,

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I'm going to just ignore this

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and I'm going to start printing.

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So using or is a little bit more efficient.

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But again, it depends on what you need.

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If you need to check

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if both is friend and is user is true,

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you'll have to use and.

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But this works both ways with and as well.

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For example, if is friend is false,

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this is going to get short circuited

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because I'm going to say, hey, if is friend is false,

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well I don't really care what is user is

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because there's no way that both of these are true.

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I've already seen that one of them is false.

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So I'm going to ignore this and I'm going to print this.

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And when I say I,

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I mean our good old friend Python interpreter.

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Now this topic of short circuiting doesn't really get taught

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in beginner Python courses.

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But now if you hear this

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maybe you hear this in an interview.

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As you can see it sounds a lot more difficult

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than it actually is.

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And frankly it makes a lot of sense, right?

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We want our machines to be efficient

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and it is quite efficient due to short circuiting.

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I'll see you in the next one.

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Bye bye.