18.2: Boolean Expressions
- Page ID
- 15377
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A boolean expression is an expression that is either true or false. The following examples use the operator ==, which compares two operands and produces True if they are equal and False otherwise:
>>> 5 == 5 True >>> 5 == 6 False
True and False are special values that belong to the type bool; they are not strings:
>>> type(True) <type 'bool'> >>> type(False) <type 'bool'>
The == operator is one of the relational operators; the others are:
x != y # x is not equal to y
x > y # x is greater than y
x < y # x is less than y
x >= y # x is greater than or equal to y
x <= y # x is less than or equal to y
Although these operations are probably familiar to you, the Python symbols are different from the mathematical symbols. A common error is to use a single equal sign (=) instead of a double equal sign (==). Remember that = is an assignment operator and == is a relational operator. There is no such thing as =< or =>.