Python 3.8正式发布,来尝鲜这些新特性吧

In : (lambda f: f(f, int(input('Input: ')), 1, 0, 1))(lambda f, t, i, a, b: print(f'fib({i}) = {b}') or t == i or f
 ...: (f, t, i + 1, b, a + b))
Input: 10
fib(1) = 1
fib(2) = 1
fib(3) = 2
fib(4) = 3
fib(5) = 5
fib(6) = 8
fib(7) = 13
fib(8) = 21
fib(9) = 34
fib(10) = 55
Out: True

In : [(t:=(t[1], sum(t)) if i else (0,1))[1] for i in range(10)]
Out: [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
PEP 570: Python Positional-Only parameters

In : import sys
...: import urllib.request
...:
...:
...: def audit_hook(event, args):
...: if event in ['urllib.Request']:
...: print(f'Network {event=} {args=}')
...:
...: sys.addaudithook(audit_hook)

In : urllib.request.urlopen('https://httpbin.org/get?a=1')
Network event='urllib.Request' args=('https://httpbin.org/get?a=1', None, {}, 'GET')
Out: <http.client.HTTPResponse at 0x10e394310>

In : def audit_hook(event, args):
...: if event in ['make_request']:
...: print(f'Network {event=} {args=}')
...:

In : sys.addaudithook(audit_hook)

In : sys.audit('make_request', 'https://baidu.com')
Network event='make_request' args=('https://baidu.com',)

In : sys.audit('make_request', 'https://douban.com')
Network event='make_request' args=('https://douban.com',)
Multiprocessing shared memory

# IPython进程A
In : from multiprocessing import shared_memory

In : a = shared_memory.ShareableList([1, 'a', 0.1])

In : a
Out: ShareableList([1, 'a', 0.1], name='psm_d5d6ba1b') # 注意name
# IPython进程B(另外一个终端进入IPython)
In : from multiprocessing import shared_memory

In : b = shared_memory.ShareableList(name='psm_d5d6ba1b') # 使用name就可以共享内存

In : b
Out: ShareableList([1, 'a', 0.1], name='psm_d5d6ba1b')
New importlib.metadata module

In : from importlib.metadata import version, files, requires, distribution

In : version('flask')
Out: '1.1.1'

In : requires('requests')
Out:
['chardet (<3.1.0,>=3.0.2)',
 'idna (<2.9,>=2.5)',
 'urllib3 (!=1.25.0,!=1.25.1,<1.26,>=1.21.1)',
 'certifi (>=2017.4.17)',
 "pyOpenSSL (>=0.14) ; extra == 'security'",
 "cryptography (>=1.3.4) ; extra == 'security'",
 "idna (>=2.0.0) ; extra == 'security'",
 "PySocks (!=1.5.7,>=1.5.6) ; extra == 'socks'",
 'win-inet-pton ; (sys_platform == "win32" and python_version == "2.7") and extra == \'socks\'']

In : dist = distribution('celery')

In : dist.version
Out: '4.3.0'

In : dist.metadata['Requires-Python']
Out: '>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'

In : dist.metadata['License']

In : dist.entry_points
Out:
[EntryPoint(name='celery', value='celery.__main__:main', group='console_scripts'),
 EntryPoint(name='celery', value='celery.contrib.pytest', group='pytest11')]

In : files('celery')[8]
Out: PackagePath('celery/__init__.py')

In : dist.locate_file(files('celery')[8])
Out: PosixPath('/Users/dongweiming/test/venv/lib/python3.8/site-packages/celery/__init__.py')
functools.cached_property

In : @lru_cache()
...: def add(a, b):
...: return a + b
...:

In : @lru_cache
...: def add(a, b):
...: return a + b
...:

@dataclass
class InventoryItem:
 ...

def dataclass(cls=None, /, *, init=True, repr=True, eq=True, order=False,
 unsafe_hash=False, frozen=False):

In : import asyncio

In : from unittest.mock import AsyncMock, MagicMock

In : mock = AsyncMock(return_value={'json': 123})
In : await mock()
Out: {'json': 123}

In : asyncio.run(mock())
Out: {'json': 123}

In : async def main(*args, **kwargs):
...: return await mock(*args, **kwargs)
...:

In : asyncio.run(main())
Out: {'json': 123}

In : mock = MagicMock() # AsyncMock也可以

In : mock.__aiter__.return_value = [1, 2, 3]

In : async def main():
...: return [i async for i in mock]
...:

In : asyncio.run(main())
Out: [1, 2, 3]
Generalized iterable unpacking in yield and return