Conditional Expressions
In this video, you’ll meet the Conditional Expression, which is some sort of one-line if-else
-statement.
The basic syntax is as follows:
<statement1> if <expr> else <statement2>
00:00 Section 4: Conditional Expressions. Conditional expressions are slightly confusing at first. They kind of look like a one-liner, but they’re written differently.
00:12
If it helps, you can think of them as a one-line if
/else
statement. Think back to the if
/else
syntax.
00:21
A conditional expression is just taking this syntax and streamlining it so it looks like this. You can see now the expression sits in the middle, <statement1>
comes first if <expr>
is True
, or else
we use <statement2>
. You’ll see this most often used as a way to assign variables based on the results of a comparison.
00:48
Let’s hop into the console and I’ll show you what that looks like. We need a variable or something to compare in our conditional expression, so let’s give it dog_lover
is True
. And let’s set up another variable.
01:10
Let’s say you want to use a conditional expression to assign this variable, buy_a_dog
. We need our first statement, which will just simply be "Yes" if dog_lover
—if dog_lover
evaluates to True
—else "Nope"
, we’re not going to buy a dog.
01:36
So, see if you can work this out in your head real quick and then press Enter. Oh, I’m missing the r
on dog_lover
. Let’s try that again.
01:47
And now I’ll hit Up arrow twice to get back to my conditional. Now let’s see what the buy_a_dog
variable contains.
01:57
We get 'Yes'
. If I switch dog_lover
to False
and run the conditional expression again, buy_a_dog
will be 'Nope'
.
02:10 That’s it for conditional expressions, my friend. See you in the next one!
smohankumar7 on May 21, 2022
yes, please correct it
![Avatar image for Martin Breuss](/cdn-cgi/image/width=500,height=500,fit=crop,gravity=auto,format=auto/https://files.realpython.com/media/martin_breuss_python_square.efb2b07faf9f.jpg)
Martin Breuss RP Team on May 22, 2022
The lesson is updated now, thanks for the heads-up Zarata and smohankumar7 :)
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Zarata on April 7, 2020
Oops. Your one slide states:
You’re fine in the example block above this comment :)