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What are Logical Operators?
and and or or not
Before, we've seen mathematical operators like
+, - and %. We know about relational operators like ==, >=, <=, >, < and so on, that compare two values to each other. Now, we learn how to string together many of these conditions to create compound condition statements.First, we'll discuss how the three basic logical operators work:
not, or and and.The
not operator does not change the way control flows, which is why we discuss it first. It changes a Truth-y value to a False-y one, and vice-versa.>>> not True
False
>>> not False
True
>>> not "61a"
False
>>> not []
True
>>> not (200 == 300)
True
The
or operator returns the first Truth-y value it finds, or — in case no Truth-y value is found — the last False-y value it finds.>>> 1 or 2
1
>>> 0 or 1
1
>>> 0 or None
None
>>> 0 or None or 1
1
The
and operator returns the first False-y value it finds, or — in case no False-y value is found — the last Truth-y value it finds.>>> 1 and 2
2
>>> 0 and 1
0
>>> None and 0
None
>>> 0 and None and 1
0
Notice how
and and or behave complimentarily from each other!So what is so special about
and and or? Here's the special thing — when they find their first False-y and first Truth-y value respectively, they return that value and do not keep reading that sentence!Let's take an example:
>>> 0 or 1 or 1/0
1
We know that 1/0 typically throws a
Division by Zero Error. However, this statement does not do so! Instead, it finds the first Truth-y value — 1 — and returns it, not even reading the 1/0 at the end of the expression.Let's also take a similar example for
and:>>> 1 and 0 and 1/0
0
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