![]() In that case, the value of the second input would be needed for the result of and. In contrast, True and inverse_and_true(0) would raise an exception. Because of short-circuit evaluation, the function isn’t called, the division by 0 doesn’t happen, and no exception is raised. However, the last line doesn’t raise an exception. ![]() It does serve the purpose of neatly failing when given 0 as a parameter since division by 0 is invalid. The function inverse_and_true() is admittedly silly, and many linters would warn about the expression 1 // n being useless. > inverse_and_true ( 5 ) True > inverse_and_true ( 0 ) Traceback (most recent call last):įile "", line 2, in inverse_and_true ZeroDivisionError: integer division or modulo by zero > False and inverse_and_true ( 0 ) False In the most extreme cases, the correctness of your code can hinge on the short-circuit evaluation. In other cases, such as when it would be computationally intensive to evaluate expressions that don’t affect the result, it provides a significant performance benefit. In some cases, it might have little effect on your program. The importance of short-circuit evaluation depends on the specific case. In those cases, the other input is not evaluated. These specifications are called truth tables since they’re displayed in a table.Īs you’ll see later, in some situations, knowing one input to an operator is enough to determine its value. Since Python Boolean values have only two possible options, True or False, it’s possible to specify the operators completely in terms of the results they assign to every possible input combination. You’ll see how this generalizes to other values in the section on truthiness. For now, all examples will use Boolean inputs and results. Note: Later, you’ll see that these operators can be given other inputs and don’t always return Boolean results. Boolean Operatorsīoolean operators are those that take Boolean inputs and return Boolean results. This is a useful way to take advantage of the fact that Booleans are numbers. The word "the" appears in half the lines in the selection. Now, if you divide that result by 4, the length of the list, you get 0.5. When you add False True True False, you get 2. Since is a list of four Booleans, you can add them together. Since Booleans are numbers, you can add them to numbers, and 0 False True gives 1. In the second line, "the" does appear, so "the" in line_list is True. The first line doesn’t have the word "the" in it, so "the" in line_list is False. The line_list variable holds a list of lines. splitlines () > "the" in line_list False > "the" in line_list True > 0 False True # Equivalent to 0 0 1 1 > False True True False 2 > len ( line_list ) 4 > 2 / 4 0.5 ![]() Example: "cats NEAR kittens" would return only results that contain both terms in close proximity to each other.> lines = """ \. NEAR means that the search engine searches for information related to all keywords found within a certain number of words (which can vary depending on search algorithms) from each other.Example: "cats OR kittens" broadens the search operation by combining all the terms, and returning results that contain either term. OR means that the search engine will search for information related to all keywords the user has typed.Example: "cats NOT kittens" means that it returns only results with the term "cats" that do not contain the term "kittens" as well. Example: If the user specifies "cats AND kittens," then it returns only results containing both terms. When using the Boolean search method, one can either use the words or their equivalent mathematical symbol, as given below: A Boolean search, which is derived from the famous Boolean logic developed by George Boole, an English mathematician in the 19th century, is useful in internet and database searches.
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