After you enter something, you get out of the loop. 发布于 2016-05-21. In this example, we will use Python not logical operator in the boolean expression of Python IF. In that case, as x = 10 so it is True. The expression not x means if x is True or False. If the condition is initially false, the loop body will not be executed at all. Empty strings in Python are evaluated as false, so the use of 'not' make it true; therefore, you get in the loop, and until you've not entered anything, you're still in the loop. Python not: If Not TrueApply the not-operator to see if an expression is False. While loops, like the ForLoop, are used for repeating sections of code - but unlike a for loop, the while loop will not run n times, but until a defined condition is no longer met. A shadow is the absence of light. The syntax for not equal in Python. With this keyword we change the meaning of expressions. Python Program #not boolean value a = False if not a: print('a is false.') The syntax of a while loop in Python programming language is −. Browse other questions tagged python-3.x while-loop range or ask your own question. The Overflow Blog Podcast 300: Welcome to 2021 with Joel Spolsky There are two ways to write the Python not equal comparison operator:. Usage in Python. While loops. A while loop might not even execute once if the condition is not met. While. Python While Loops Previous Next Python Loops. name 是 True, not name 是false name是 False, not name是True. Example. Most developers recommend sticking with != in Python, because both Python 2 and Python 3 support this syntax.>, however, is deprecated in Python 3, and only works in older versions: Print i as long as i is less than 6: i = 1 while i 6: print(i) i += 1 Python has two primitive loop commands: while loops; for loops; The while Loop. Keyword info. In spite of being present in most of the popular programming languages, Python does not have a native do-while statement. In Python, if a variable is a numeric zero or empty, or a None object then it is considered as False, otherwise True. With the while loop we can execute a set of statements as long as a condition is true. Code faster with the Kite plugin for your code editor, featuring Line-of-Code Completions and cloudless processing. Not. #!/usr/bin/python count = 0 while count < 5: print count, " is less than 5 " count = count + 1 else: print count, " is not less than 5 " 以上实例输出结果为： 0 is less than 5 1 is less than 5 2 is less than 5 3 is less than 5 4 is less than 5 5 is not less than 5 So We can use the else-statement, after the main part of a while-loop, to catch these situations. When do I use them? The condition may be any expression, and true is any non-zero value. 学习PYTHON基础教程 看到” while not name:" 这个怎么理解 ... name这个值是空的时候,while才循环运行. while expression: statement(s) Here, statement(s) may be a single statement or a block of statements. While continues until a terminating condition is met. dot net perls. dot net perls. As x is True, so not operator evaluated as False and else part executed. Python while Loop ExamplesUnderstand the while-loop. #not boolean condition a = 5 if not a==5: print('a is not 5') else: print('a is 5') Consider the "not" keyword in Python. Kite is a free autocomplete for Python developers. A while loop statement in Python programming language repeatedly executes a target statement as long as a given condition is true.. Syntax. The statements within the while are not reached. Invert the value of booleans. However, do-while will run once, then check the condition for subsequent loops.