python 手动迭代iter/next

• 2019 年 10 月 11 日
• 筆記

with open('/etc/passwd') as f:   while True:   line = next(f, None)   if line is None:   break   print(line, end='')

 items = [1, 2, 3]   Get the iterator   it = iter(items) # Invokes items.iter()   Run the iterator   next(it) # Invokes it.next()   1   next(it)   2   next(it)   3   next(it)   Traceback (most recent call last):   File "<stdin>", line 1, in <module>   StopIteration

类实现迭代iter

class Node: def init(self, value): self._value = value self._children = []

def __repr__(self):      return 'Node({!r})'.format(self._value)    def add_child(self, node):      self._children.append(node)    def __iter__(self):      return iter(self._children)

Example

if name == 'main': root = Node(0) child1 = Node(1) child2 = Node(2) root.add_child(child1) root.add_child(child2) # Outputs Node(1), Node(2) for ch in root: print(ch