try:
    1 / 0
except ZeroDivisionError:
    raise ValueError('Zero!')

(most recent call last):
  File "test.py", line 2, in <module>
    1 / 0
ZeroDivisionError: division by zero

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 4, in <module>
    raise ValueError('Zero!')
ValueError: Zero!

division_error = None

try:
    1 / 0
except ZeroDivisionError as e:
    division_error = e

raise ValueError('Zero!') from division_error

(most recent call last):
  File "test.py", line 4, in <module>
    1 / 0
ZeroDivisionError: division by zero

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "test.py", line 8, in <module>
    raise ValueError('Zero!') from division_error
ValueError: Zero!

>>> bool(datetime(2018, 1, 1).time())
False
>>> bool(datetime(2018, 1, 1, 13, 12, 11).time())
True

def create(created_time=None) -> None:
    if not created_time:
        created_time = datetime.now().time()

def create(created_time=None) -> None:
    if created_time is None:
        created_time = datetime.now().time()

async with aiofiles.open('filename', mode='r') as f:
    contents = await f.read()

>>> int("10")
10
>>> int("10", 2)
2
>>> def base2(x):
...     return int(x, 2)
...
>>> base2("10")
2

base2 = partial(int, base=2)

>>> map(partial(int, base=2), ["1", "10", "100"])
[1, 2, 4]

>>> map(lambda x: int(x, base=2), ["1", "10", "100"])
[1, 2, 4]

package_broken = any(
    part.is_broken() for part in package.get_parts()
)
package_ok = all(
    part.ok() for part in package.get_parts()
)

from contextlib import contextmanager

QUIT_MESSAGE = 'Bye'

def print_quit_mesage():
    global QUIT_MESSAGE
    print(QUIT_MESSAGE)

@contextmanager
def global_variable_changed(name, value):
    orig_value = globals()[name]
    globals()[name] = value
    yield
    globals()[name] = orig_value

with global_variable_changed(
    'QUIT_MESSAGE',
    'Tschüss'
):
    print_quit_mesage()

>>> dict(a=1, b=2)
{'a': 1, 'b': 2}
>>> {'a': 1, 'b': 2}
{'a': 1, 'b': 2}

>>> dict(a=1)
{'a': 1}
>>> dict(1='a')
  File "<stdin>", line 1
SyntaxError: keyword can't be an expression

>>> {'a': 1, 'a': 1}
{'a': 1}
>>> dict(a=1, a=1)
  File "<stdin>", line 1
SyntaxError: keyword argument repeated

>>> d = dict(b=2)
>>> dict(a=1, **d)
{'a': 1, 'b': 2}

>>> dict(b=3, **d)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: type object got multiple values for keyword argument

{**{'a': 1}, 'b': 2, **{'c': 3}}
# Результат: {'a': 1, 'b': 2, 'c': 3}

[1, 2, *[3, 4]]
# Результат: [1, 2, 3, 4]

{**{'a': 1, 'b': 1}, 'a': 2, **{'b': 3}}
# Результат: {'a': 2, 'b': 3}

import asyncio

class Slow:
    def __init__(self, delay):
        self._delay = delay

    async def __aenter__(self):
        await asyncio.sleep(self._delay / 2)

    async def __aexit__(self, *exception):
        await asyncio.sleep(self._delay / 2)

async def main():
    async with Slow(1):
        print('slow')

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

import asyncio
from contextlib import asynccontextmanager

@asynccontextmanager
async def slow(delay):
    half = delay / 2
    await asyncio.sleep(half)
    yield
    await asyncio.sleep(half)

async def main():
    async with slow(1):
        print('slow')

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

>>> d = dict(a=1, b=2, c=3)
>>> assert d['a'] == 1
>>> assert d['c'] == 3

>>> assert d == dict(a=1, b=ANY, c=3)

>>> class AnyClass:
...     def __eq__(self, another):
...         return True
... 
>>> ANY = AnyClass()

In : eng = ['one', 'two', 'three']
In : ger = ['eins', 'zwei', 'drei']
In : for e, g in zip(eng, ger):
    ...:     print('{e} = {g}'.format(e=e, g=g))
    ...:

one = eins  
two = zwei  
three = drei

In : list(zip(*zip(eng, ger)))
Out: [('one', 'two', 'three'), ('eins', 'zwei', 'drei')]

flatten = lambda lst: [x for sub in lst for x in (flatten(sub) if isinstance(sub, list) else [sub])]

memoize = lambda f: (lambda *args, _cache={}, **kwargs: _cache.setdefault((args, tuple(kwargs.items())), f(*args, **kwargs)))

chunked = lambda lst, n: [lst[i:i+n] for i in range(0, len(lst), n)]

uniq = lambda seq: list(dict.fromkeys(seq))

deep_get = lambda d, *keys: __import__('functools').reduce(lambda a, k: a.get(k) if isinstance(a, dict) else None, keys, d)

pretty_json = lambda obj: __import__('json').dumps(obj, ensure_ascii=False, indent=2)

tail = lambda f, n=10: list(__import__('collections').deque(open(f), maxlen=n))

sh = lambda cmd: __import__('subprocess').run(cmd, shell=True, check=True, capture_output=True).stdout.decode().strip()

path_join = lambda *p: __import__('os').path.join(*p)

group_by = lambda seq, key: {k: [d for d in seq if d.get(key) == k] for k in set(d.get(key) for d in seq)}

def x():
    ...

$ cat test.py
with open('/tmp/test', 'w') as f:
    f.write('test')
$ strace python test.py 2>&1 | grep open | tail -n 1
open("/tmp/test", O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = 3

$ strace python -c 'input()'
...
read(0,

>>> exit
Use exit() or Ctrl-D (i.e. EOF) to exit
>>> str(exit)
'Use exit() or Ctrl-D (i.e. EOF) to exit'

>>> try:
...     exit()
... except:
...     'Nothing'
...
'Nothing'

$ python3
Python 3.4.3 (default, Apr 28 2015, 13:37:07)
[GCC 4.8.3 20140911 (Red Hat 4.8.3-9)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> try:
...     os._exit(42)
... finally:
...     print('Bye!')
...
$ ...

$ echo '{"a": [], "b": "c"}' | python -m json.tool
{
    "a": [],
    "b": "c"
}