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Engineering LibreTexts

3.1: Boolean Expressions

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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
    >>> 5 == 6

    True and False are special values that belong to the class bool; they are not strings:

    >>> type(True)
    <class 'bool'>
    >>> type(False)
    <class 'bool'>

    The == operator is one of the comparison 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
          x is y               # x is the same as y
          x is not y           # x is not the same as y

    Although these operations are probably familiar to you, the Python symbols are different from the mathematical symbols for the same operations. 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 comparison operator. There is no such thing as =< or =>.

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