Python for Absolute Beginners Transcripts
Chapter: Code that interacts with users
Lecture: Concept: Truthiness
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We saw the values that go into
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the if statement or elif statement
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or even the While statement have
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to evaluate to True or False.
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So let's talk about this idea of truthyness.
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That maybe sounds like a weird word
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that doesn't quite make sense
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but the idea is that different types of data
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can say for certain values I want you as far
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as the execution goes as far
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as the conditional blocks to go
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we treat this is True and this is False.
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So for example if you have just have the word False
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well then obviously that's False
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that is what the definition of False
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is in the programming language.
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But if you have a list and it has no data in it
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well then that's considered False
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but if it has like one, one, and seven.
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It has some data in it then it's True.
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if you have something called a dictionary
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or a set those are the same kind of rules.
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if you have a string well empty strings are False
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but non empty strings like "Hello"
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that's a True statement.
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So this is a little bit of a weird idea at first
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the idea is instead of trying to come up with some
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kind of test like is the length of the number
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of items in the list equal to 0, yes or no?
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You can just say if the list
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so it simplifies these tests.
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Also for numbers if there's 0 that's False
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otherwise they're True
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and then none is a way to say this
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variable has no value at the moment.
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That's also False.
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if it's not one of these things in the list
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then it's True.
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So we'll see an example of this in just a second
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but this is leveraged all over Python
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if you've got numbers you've got collections
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you've got strings, very often the way you test
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whether they're empty or not
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or their have decent values in them or not
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is to just do if the variable, carry on.
