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. With this keyword we change the meaning of expressions. Consider the "not" keyword in Python. Print i as long as i is less than 6: i = 1 while i 6: print(i) i += 1 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: 发布于 2016-05-21. The syntax for not equal in Python. Code faster with the Kite plugin for your code editor, featuring Line-of-Code Completions and cloudless processing. The expression not x means if x is True or False. Python has two primitive loop commands: while loops; for loops; The while Loop. dot net perls. While loops. Invert the value of booleans. Python Program #not boolean value a = False if not a: print('a is false.') Kite is a free autocomplete for Python developers. The Overflow Blog Podcast 300: Welcome to 2021 with Joel Spolsky A while loop statement in Python programming language repeatedly executes a target statement as long as a given condition is true.. Syntax. Python not: If Not TrueApply the not-operator to see if an expression is False. So We can use the else-statement, after the main part of a while-loop, to catch these situations. If the condition is initially false, the loop body will not be executed at all. The condition may be any expression, and true is any non-zero value. However, do-while will run once, then check the condition for subsequent loops. Python while Loop ExamplesUnderstand the while-loop. The statements within the while are not reached. Usage in Python. name 是 True, not name 是false name是 False, not name是True. #!/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 As x is True, so not operator evaluated as False and else part executed. while expression: statement(s) Here, statement(s) may be a single statement or a block of statements. A shadow is the absence of light. In spite of being present in most of the popular programming languages, Python does not have a native do-while statement. Not. In that case, as x = 10 so it is True. When do I use them? While. A while loop might not even execute once if the condition is not met. The syntax of a while loop in Python programming language is −. Python While Loops Previous Next Python Loops. #not boolean condition a = 5 if not a==5: print('a is not 5') else: print('a is 5') 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. 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. While continues until a terminating condition is met. There are two ways to write the Python not equal comparison operator:. dot net perls. Keyword info. In this example, we will use Python not logical operator in the boolean expression of Python IF. Example. After you enter something, you get out of the loop. Browse other questions tagged python-3.x while-loop range or ask your own question. 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.

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