Boolean is a fancy word for "true or false." Boolean operators are a special class of operators that are used to check whether an expression is true or false. These are especially used for comparisons.
Boolean operators in Python include < (less than), > (greater than), <= (less than or equal to), >= (greater than or equal to), == (equals), != (does not equal), & (AND), | (OR), and ! (NOT).
You can use boolean operators with numbers:
2 < 3
4 >= 8
1.0 == 1returns True, False, and True, respectively (notice that 1 and 1.0 are different types but are still considered equivalent),
expressions:
(2 + 3) != 6returns True,
even strings:
"String that I have" == "String that I am searching for"returns False.
The logical operators (&, |, and !, specifically) add an extra layer of complication.
& (AND) returns True only if the expressions on both sides are true. | (OR) refers to "logical or," meaning that it returns True if one or both of the compared expressions are true.
! (NOT) is probably the most confusing. It does not actually compare two expressions; instead, it inverts the value of the expression it is attached to (that is, !True returns False, and !False returns True).
See if you can guess what these will return without running them (but go ahead and run them if you need to).
(1 < 3) & (2*3 == 3*2)
False | True
!(2 < 2)
((2 < 4) & !(1+1 == 3)) | !((16%2 > 0) & (10+10+10+10 <= 4*10) & False)Sorry for the last one; they're just super important.
Okay, on to 04_lists-and-iteration.md!