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python基础--异常，对象和迭代器

2024-09-21 21:01:23   207人阅读

  • 异常处理
  • 面向对象
  • 迭代器和生成器

python异常处理

  • 下面代码触发了一个FileNotFoundError
>>> open("notexist.txt")Traceback (most recent call last):  File "<stdin>", line 1, in <module>FileNotFoundError: [Errno 2] No such file or directory: ‘notexist.txt‘
  • 抛出异常
>>> raise FileNotFoundError
  • 异常类型

技术分享

  • 捕获异常使用try,except,finally,else
try:  open(r"c:\Users\kingsoft\Desktop\notexist.txt")except FileNotFoundError as e:  print ("file not exist...")except (name1,name2):  print ("io error is true...")else:  print ("file exist..")finally:  print ("always do...")

　　

python面向对象

python是完全面向对象的，python中一切都是对象，包括变量，函数等。

  • 定义一个对象
class MyException():	pass
  • self 和init方法
class Person():	def __init__(self, name):		self.name = name			def sayname(self):		print self.namem = Person("joe")print(m.sayname())
  • 区分类和类的实例
class Person():	def __init__(self, name):		self.name = name			Person.name = name	def sayname(self):		print("myname is :" + self.name)		print("myexceptionname is: " + Person.name)	def changeothername(self, name):		Person.name = name	def __del__(self):		print(self.name + "is gone")m = Person("joe")m.sayname()print("m.name : " + m.name)m.test="tt"print(m.test)j = Person("jason")j.sayname()j.changeothername(j.name)m.sayname()
  • 类的继承，多态和封装概念

生成器和迭代器

  • _iter_方法返回迭代器，迭代器指有next方法的对象
class Fibs(object):	"""docstring for Fibs"""	def __init__(self, max):		self.max = max		self.a = 0		self.b = 1	def __next__(self):		fib = self.a		if fib > self.max:			raise StopIteration		self.a, self.b = self.b, self.a + self.b		return fib	#返回迭代器	def __iter__(self):		return selffib = Fibs(1000)for f in fib:	print(f, end= " ")
  • 可迭代对象Iterable和迭代器Iterator
  • 生成器，生成器通过yield语句快速生成迭代器，让函数变成一个生成器
#斐波那契数列def getfibs(max):	a = 0	b = 1	while a < max:		a, b= b, a+b		value = http://www.mamicode.com/a>
  • 简单理解生成器
def gen():	yield "hello"	yield "how"	yield "are"	yield "you"for i in gen():	print(i)

　　

python基础--异常，对象和迭代器


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