Original subtitles

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Now up to this point, you've seen us use if statements,

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else statements, elif statements,

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multiple if statements as well as nested if statements.

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But the thing that we haven't been able to do thus far is to check for multiple

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conditions in the same line of code.

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So how would we be able to combine different conditions and say, well,

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is the pizza large and the user wants pepperoni and extra cheese all in the

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same line of code? Well,

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to do this we would need to learn about the logical operators.

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So there's three of them that are really useful: and, or and not.

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So let's take a look at the first one.

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When you combine two different conditions using an and operator,

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they both have to be true,

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both A and B for the entire line of code to be true.

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If just one of them is true, say A is true and B is false,

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or A is false and B is true, then the overall thing evaluates to false.

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So if we take a look just inside the console,

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and in fact, I'm going to clear the console, and I write some code here.

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Let's say that, um,

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A = 12 right? Now let's say that I wanted to check whether if is A greater

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than 15? Well that is going to be false.

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Now what about is A greater than 10? Well,

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that's going to be true.

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Now if I combined this using an and statement, I could say,

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well is A greater than 10 and A is less than 13 and hit enter, then I would get

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true because both A is greater than 10 and A is less than 13 are true.

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So in this case, when both conditions are true,

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then this entire line gets evaluated to true.

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But see what happens when just one of them is false.

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So is A greater than 15 and A less than 13? A is greater than 15 is false,

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A is less than 13 is true and now we get false.

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So that's what happens when you combine different conditions using and. Now if

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you only needed one of the conditions to be true,

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then you could use the or operator instead.

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So if a C or D were true or if they're both true,

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then it'll evaluate to true.

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It's only when both C and D are false

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does this statement actually become false.

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Now the final one is the not operator and all that this does is it basically

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reverses a condition. So if the condition is false,

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then it becomes true. If it's true, then it becomes false.

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If I wrote not

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and then I wrote the condition A is greater than 15. A greater than 15 is

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definitely false, 12 is less than 15. But by putting the not there

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it's going to reverse this, so going from false to true.

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So when I hit enter, you'll see it is now true.

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Coming back to our rollercoaster ticketing,

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let's say that the rollercoaster company decided that for everybody who was

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having a midlife crisis, they would give them free tickets.

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And according to Wikipedia,

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midlife crises typically occur when you're a 45 to 55 years old.

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Let's see if we can incorporate this into our code.

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So let's say that in addition to these existing price categories,

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what if you had to add a separate price category for those people who are aged

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between 45 and 55 and those people get to ride for free?

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Do you think you would be able to change the code using what you've learned

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about logical operators in order to incorporate this addition to our program?

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Pause the video and give that a go.

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So we've currently got three conditions: age,

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less than 12, age between 12 and 18, and finally everybody else.

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Now instead of just finishing up there,

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let's go ahead and add another elif.

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And here we're going to combine two conditions.

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We're going to say if the age is greater than or equal to 45 and the age is less

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than or equal to 55, then we get to catch that midlife crisis window.

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Well,

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in this case, we're going to print something like-- we're going to say "Everything's

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going to be ok. Have a free ride on us!"

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And in fact,

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we don't need to modify the bill in any way because we know that with

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if, elif and else statements is that once this condition matches,

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then everything that's inside this block,

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so everything that's indented inside this elif is going to be carried out

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namely printing this out,

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and then it's going to skip the rest of this if/else block and continue on.

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Now, if they want to photo this,

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they'll have to pay $3 but at least their ticket is free.

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And we've been able to do this because we know about the and logical operator.

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In the next lesson,

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we're going to practice using logical operators and more by completing another

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code challenge. So for all of that and more, I'll see you there.