![]() For CS106A, you don't ever need to use this shorthand, but it's there if you want to use it. Testing for "empty" data is such a common case, it's nice to have a shorthand for it. Why does the truthy system exist? It makes it easy to test, for example, for an empty string like the following. > bool('False') # tricky: what's this one? The int 6 or the non-empty string 'hi', or the list all count as True.Īny value and returns a formal bool False/True value, so it's a way for us to see how truthy logic works in the interpreter: When an if-test expression is something like 0 or None or the empty string '', that counts as False. All the sort of "empty" values count as False: 0, 0.0, None, '',, The truthy rules define a series of values which count as False. What does s mean as an if-test? Python has rules for this we'll call "truthy" logic. We think of if/while tests as looking at boolean values, however the rules are flexible so any type can work in there. You can use else if you prefer, just thinking about possible alternative structure here. # notice: no if-else structure, not indented down here # rest of computation having screened out too-short and too-long > 'apple' > 'apple' high and s != 'alice':Īnswer: c happens when s is not 'bob' but also (score 100: The interpreter examples below shows various = style comparisons and their boolean results: != not-equal, the opposite of equal (uses = under the hood) Not recommended to use with float values. = test if two values are equal (2 equals signs together). the comparison expression num = 6 evaluates to True when num is 6 and False otherwise. The most common way to get a boolean True/False is comparing two values, e.g. ![]() To run code if a test is False and otherwise do nothing, use not like this: Use regular if to do action-1 or nothing. Use else: if the run should choose between either action-1 or action-2 depending on the test, but not do nothing. The optional else: part of an if-statement adds code to run in the case that the test is False. Instead, let the if/while take the boolean value directly like this: Suppose some foo() function is supposed to return True or False. It returns either true or false depending on the result of the operation. It's very easy to accidentally type a single equal sign for a comparison like the following, but in Python that is flagged as a syntax error: The not equal operator is a relational or comparison operator that compares two or more values (operands). The if-statement uses comparisons like i > for num in : ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |