import time
from collections import Iterable
from collections import Iterator
# 有__iter__方法的类是Iterable(可迭代的)。
# 既有__iter__方法又有__next__方法是Iterator(迭代器)。
class Classmate(object):
  def __init__(self):
    self.names = list()
    self.current_num = 0
  def add(self, name):
    self.names.append(name)
  def __iter__(self):
    """Iterable对象必须实现__iter__方法"""
    return self # __iter__方法必须返回一个Iterator(既有__iter__方法,又有__next__方法)
  # __next__的返回值就是for循环遍历出的变量值
  def __next__(self):
    if self.current_num < len(self.names):
      ret = self.names[self.current_num]
      self.current_num += 1
      return ret
    else:
      raise StopIteration # 抛出StopIteration异常时,for遍历会停止迭代
classmate = Classmate()
classmate.add("老王")
classmate.add("王二")
classmate.add("张三")
# print("判断classmate是否是可以迭代的对象:", isinstance(classmate, Iterable))
# classmate_iterator = iter(classmate) # iter()会调用对象的__iter__方法
# print("判断classmate_iterator是否是迭代器:", isinstance(classmate_iterator, Iterator))
# print(next(classmate_iterator))  # next()会调用对象的__next__方法
for name in classmate: # 遍历时会先调用classmate的__iter__方法(必须返回Iterator对象)。
  print(name)  # 遍历出的name就是返回的Iterator对象的__next__方法的返回值
  time.sleep(1) # 当__next__抛出StopIteration异常时,for遍历会停止迭代

class Classmate(object):
  def __init__(self):
    self.names = list()
    self.current_num = 0
  def add(self, name):
    self.names.append(name)
  def __iter__(self):
    """Iterable对象必须实现__iter__方法"""
    return self # __iter__方法必须返回一个Iterator(既有__iter__方法,又有__next__方法)
  # __next__的返回值就是for循环遍历出的变量值
  def __next__(self):
    if self.current_num < len(self.names):
      ret = self.names[self.current_num]
      self.current_num += 1
      return ret
    else:
      raise StopIteration # 抛出StopIteration异常时,for遍历会停止迭代
classmate = Classmate()
classmate.add("老王")
classmate.add("王二")
classmate.add("张三")
li = list(classmate)  # 将可迭代对象转换成list类型。 底层就是通过迭代实现的。
print(li)

class Classmate(object):
  def __init__(self):
    self.names = list()
    self.current_num = 0
  def add(self, name):
    self.names.append(name)
  def __iter__(self):
    """Iterable对象必须实现__iter__方法"""
    return self # __iter__方法必须返回一个Iterator(既有__iter__方法,又有__next__方法)
  # __next__的返回值就是for循环遍历出的变量值
  def __next__(self):
    if self.current_num < len(self.names):
      ret = self.names[self.current_num]
      self.current_num += 1
      return ret
    else:
      raise StopIteration # 抛出StopIteration异常时,for遍历会停止迭代
classmate = Classmate()
classmate.add("老王")
classmate.add("王二")
classmate.add("张三")
tp = tuple(classmate)  # 将可迭代对象转换成tuple类型。
print(tp)