#!/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 Consider the "not" keyword in Python. 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 continues until a terminating condition is met. Python While Loops Previous Next Python Loops. 发布于 2016-05-21. Print i as long as i is less than 6: i = 1 while i 6: print(i) i += 1 The expression not x means if x is True or False. A shadow is the absence of light. while expression: statement(s) Here, statement(s) may be a single statement or a block of statements. The syntax of a while loop in Python programming language is −. After you enter something, you get out of the loop. #not boolean condition a = 5 if not a==5: print('a is not 5') else: print('a is 5') Usage in Python. Not. 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: However, do-while will run once, then check the condition for subsequent loops. The Overflow Blog Podcast 300: Welcome to 2021 with Joel Spolsky The condition may be any expression, and true is any non-zero value. Python Program #not boolean value a = False if not a: print('a is false.') Browse other questions tagged python-3.x while-loop range or ask your own question. Python has two primitive loop commands: while loops; for loops; The while Loop. When do I use them? A while loop statement in Python programming language repeatedly executes a target statement as long as a given condition is true.. Syntax. Example. The syntax for not equal in Python. 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. A while loop might not even execute once if the condition is not met. So We can use the else-statement, after the main part of a while-loop, to catch these situations. 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. If the condition is initially false, the loop body will not be executed at all. Python while Loop ExamplesUnderstand the while-loop. name 是 True, not name 是false name是 False, not name是True. While. There are two ways to write the Python not equal comparison operator:. Invert the value of booleans. While loops. Kite is a free autocomplete for Python developers. 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. In spite of being present in most of the popular programming languages, Python does not have a native do-while statement. With this keyword we change the meaning of expressions. Keyword info. dot net perls. In Python, if a variable is a numeric zero or empty, or a None object then it is considered as False, otherwise True. As x is True, so not operator evaluated as False and else part executed. Python not: If Not TrueApply the not-operator to see if an expression is False. Code faster with the Kite plugin for your code editor, featuring Line-of-Code Completions and cloudless processing. The statements within the while are not reached. dot net perls. With the while loop we can execute a set of statements as long as a condition is true.