python-3.5

I've seen several basic Python 3.5 tutorials on asyncio doing the same operation in various flavours. In this code: import asyncio async def doit(i): print("Start %d" % i) await asyncio.sleep(3) print("End %d" % i) return i if __name__ == '__main__': loop = asyncio.get_event_loop() #futures = [asyncio.ensure_future(doit(i), loop=loop) for i in range(10)] #futures = [loop.create_task(doit(i)) for i in range(10)] futures = [doit(i) for i in range(10)] result = loop.run_until_complete(asyncio.gather(*futures)) print(result) All the three variants above that define the futures variable achieve the

This question already has an answer here: Type hints: solve circular dependency 2 answers I'm trying to figure out how self-reference of types work with python3's type annotations - the docs don't specify anything regarding this. As an example: from typing import TypeVar, Optional, Generic T = TypeVar('T') class Node(Generic[T]): left = None right = None value = None def __init__( self, value: Optional[T], left: Optional[Node[T]]=None, right: Optional[Node[T]]=None, ) -> None: self.value = value self.left = left self.right = right This code generates the error: Traceback (most recent call last

In Python2.7 this code can work very well, __getattr__ in MetaTable will run. But in Python 3.5 it doesn't work. class MetaTable(type): def __getattr__(cls, key): temp = key.split("__") name = temp[0] alias = None if len(temp) > 1: alias = temp[1] return cls(name, alias) class Table(object): __metaclass__ = MetaTable def __init__(self, name, alias=None): self._name = name self._alias = alias d = Table d.student__s But in Python 3.5 I get an attribute error instead: Traceback (most recent call last): File "/Users/wyx/project/python3/sql/dd.py", line 31, in <module> d.student__s AttributeError: