最常见的流程控制语句是if语句。如果语句的条件是True,那么if语句的子句(即if语句后面的块)将会执行。如果条件为False,则跳过该子句。 简单地说,if语句可以理解为,“如果这个条件为真,则执行子句中的代码”。在 Python 中,if语句由以下内容组成: if关键字 条件(即计算结果为True或False的表达式) 一个冒号 从下一
If none of our if and elif statements return true, the default condition is else. Now let's look at a modified example where we use a function that checks to see if we can read the shadow file. We test this with the os.access method. We want to know if we can read the file, ...
# Python program killing# a thread using ._stop()# functionimporttimeimportthreadingclassMyThread(threading.Thread):# Thread class with a _stop() method.# The thread itself has to check# regularly for the stopped() condition.def__init__(self,*args,**kwargs):super(MyThread,self).__init_...
self.message_queue=queue.Queue() 以下这个是引入协程的MessageBroker类: classMessageBrokerAsy:#高性能异步步消息订阅分发处理def__init__(self):self.message_queue=queue.Queue()self.subscribers={}self.thread=Noneself.running=True#self.condition = asyncio.Condition()defpublish(self,topic,message):ifself...
if name == 'Alice': print('Hi, Alice.') else: print('Hello, stranger.') 图2-3 显示了这段代码的流程图。 图2-3:一个else语句的流程图 elif语句 虽然只有if或else子句中的一个会执行,但您可能希望执行多个可能子句中的一个。elif语句是一个else if语句,总是跟在一个if或另一个elif语句之后。它...
{ key_expr: value_expr for value in collection [if condition] } 【例子】 [70]: b = {i: i % 2 == 0 for i in range(10) if i % 3 == 0} print(b) # {0: True, 3: False, 6: True, 9: False} {0: True, 3: False, 6: True, 9: False} ...
As a Python developer you can choose to throw an exception if a condition occurs. To throw (or raise) an exception, use theraisekeyword. Example Raise an error and stop the program if x is lower than 0: x = -1 ifx <0: raiseException("Sorry, no numbers below zero") ...
Stop program if condition is truthy. ./vasp/vasp_core.py::553 def stop_if(self, condition=None): """Stop program if condition is truthy.""" if condition: import sys sys.exit() Vasp.update args = (self, atoms=None) Updates calculator. If a calculation is required, run it, otherwise...
given breakpoint number. If count is omitted, the ignore count is set to 0. A breakpoint becomes active when the ignore count is zero. When non-zero, the count is decremented each time the breakpoint is reached and the breakpoint is not disabled and any associated condition evaluates to ...
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