Python for Absolute Beginners Transcripts
Chapter: Code that interacts with users
Lecture: Concept: Truthiness

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0:00 We saw the values that go into
0:02 the if statement or elif statement
0:04 or even the While statement have
0:06 to evaluate to True or False.
0:08 So let's talk about this idea of truthyness.
0:11 That maybe sounds like a weird word
0:13 that doesn't quite make sense
0:15 but the idea is that different types of data
0:17 can say for certain values I want you as far
0:20 as the execution goes as far
0:22 as the conditional blocks to go
0:24 we treat this is True and this is False.
0:27 So for example if you have just have the word False
0:29 well then obviously that's False
0:30 that is what the definition of False
0:32 is in the programming language.
0:33 But if you have a list and it has no data in it
0:36 well then that's considered False
0:38 but if it has like one, one, and seven.
0:41 It has some data in it then it's True.
0:44 if you have something called a dictionary
0:45 or a set those are the same kind of rules.
0:47 if you have a string well empty strings are False
0:51 but non empty strings like "Hello"
0:53 that's a True statement.
0:55 So this is a little bit of a weird idea at first
0:57 the idea is instead of trying to come up with some
0:59 kind of test like is the length of the number
1:02 of items in the list equal to 0, yes or no?
1:05 You can just say if the list
1:07 so it simplifies these tests.
1:09 Also for numbers if there's 0 that's False
1:12 otherwise they're True
1:13 and then none is a way to say this
1:16 variable has no value at the moment.
1:18 That's also False.
1:20 if it's not one of these things in the list
1:22 then it's True.
1:23 So we'll see an example of this in just a second
1:25 but this is leveraged all over Python
1:28 if you've got numbers you've got collections
1:30 you've got strings, very often the way you test
1:33 whether they're empty or not
1:34 or their have decent values in them or not
1:36 is to just do if the variable, carry on.