import functools
from pykka import _compat
__all__ = ['Future', 'get_all']
[docs]class Future(object):
"""
A :class:`Future` is a handle to a value which is available or will be
available in the future.
Typically returned by calls to actor methods or accesses to actor fields.
To get hold of the encapsulated value, call :meth:`Future.get` or, if
using Python 3.5+, ``await`` the future.
"""
def __init__(self):
super(Future, self).__init__()
self._get_hook = None
self._get_hook_result = None
[docs] def get(self, timeout=None):
"""
Get the value encapsulated by the future.
If the encapsulated value is an exception, it is raised instead of
returned.
If ``timeout`` is :class:`None`, as default, the method will block
until it gets a reply, potentially forever. If ``timeout`` is an
integer or float, the method will wait for a reply for ``timeout``
seconds, and then raise :exc:`pykka.Timeout`.
The encapsulated value can be retrieved multiple times. The future will
only block the first time the value is accessed.
:param timeout: seconds to wait before timeout
:type timeout: float or :class:`None`
:raise: :exc:`pykka.Timeout` if timeout is reached
:raise: encapsulated value if it is an exception
:return: encapsulated value if it is not an exception
"""
if self._get_hook is not None:
if self._get_hook_result is None:
self._get_hook_result = self._get_hook(timeout)
return self._get_hook_result
raise NotImplementedError
[docs] def set(self, value=None):
"""
Set the encapsulated value.
:param value: the encapsulated value or nothing
:type value: any object or :class:`None`
:raise: an exception if set is called multiple times
"""
raise NotImplementedError
[docs] def set_exception(self, exc_info=None):
"""
Set an exception as the encapsulated value.
You can pass an ``exc_info`` three-tuple, as returned by
:func:`sys.exc_info`. If you don't pass ``exc_info``,
:func:`sys.exc_info` will be called and the value returned by it used.
In other words, if you're calling :meth:`set_exception`, without any
arguments, from an except block, the exception you're currently
handling will automatically be set on the future.
:param exc_info: the encapsulated exception
:type exc_info: three-tuple of (exc_class, exc_instance, traceback)
"""
raise NotImplementedError
[docs] def set_get_hook(self, func):
"""
Set a function to be executed when :meth:`get` is called.
The function will be called when :meth:`get` is called, with the
``timeout`` value as the only argument. The function's return value
will be returned from :meth:`get`.
.. versionadded:: 1.2
:param func: called to produce return value of :meth:`get`
:type func: function accepting a timeout value
"""
self._get_hook = func
[docs] def filter(self, func):
"""
Return a new future with only the items passing the predicate function.
If the future's value is an iterable, :meth:`filter` will return a new
future whose value is another iterable with only the items from the
first iterable for which ``func(item)`` is true. If the future's value
isn't an iterable, a :exc:`TypeError` will be raised when :meth:`get`
is called.
Example::
>>> import pykka
>>> f = pykka.ThreadingFuture()
>>> g = f.filter(lambda x: x > 10)
>>> g
<pykka.future.ThreadingFuture at ...>
>>> f.set(range(5, 15))
>>> f.get()
[5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
>>> g.get()
[11, 12, 13, 14]
.. versionadded:: 1.2
"""
future = self.__class__()
future.set_get_hook(
lambda timeout: list(filter(func, self.get(timeout)))
)
return future
[docs] def join(self, *futures):
"""
Return a new future with a list of the result of multiple futures.
One or more futures can be passed as arguments to :meth:`join`. The new
future returns a list with the results from all the joined futures.
Example::
>>> import pykka
>>> a = pykka.ThreadingFuture()
>>> b = pykka.ThreadingFuture()
>>> c = pykka.ThreadingFuture()
>>> f = a.join(b, c)
>>> a.set('def')
>>> b.set(123)
>>> c.set(False)
>>> f.get()
['def', 123, False]
.. versionadded:: 1.2
"""
future = self.__class__()
future.set_get_hook(
lambda timeout: [f.get(timeout) for f in [self] + list(futures)]
)
return future
[docs] def map(self, func):
"""
Return a new future with the result of the future passed through a
function.
Example::
>>> import pykka
>>> f = pykka.ThreadingFuture()
>>> g = f.map(lambda x: x + 10)
>>> f.set(30)
>>> g.get()
40
>>> f = pykka.ThreadingFuture()
>>> g = f.map(lambda x: x['foo'])
>>> f.set({'foo': 'bar'}})
>>> g.get()
'bar'
.. versionadded:: 1.2
.. versionchanged:: 2.0
Previously, if the future's result was an iterable (except a
string), the function was applied to each item in the iterable.
This behavior is unpredictable and makes regular use cases like
extracting a single field from a dict difficult, thus the
behavior has been simplified. Now, the entire result value is
passed to the function.
"""
future = self.__class__()
future.set_get_hook(lambda timeout: func(self.get(timeout)))
return future
[docs] def reduce(self, func, *args):
"""
reduce(func[, initial])
Return a new future with the result of reducing the future's iterable
into a single value.
The function of two arguments is applied cumulatively to the items of
the iterable, from left to right. The result of the first function call
is used as the first argument to the second function call, and so on,
until the end of the iterable. If the future's value isn't an iterable,
a :exc:`TypeError` is raised.
:meth:`reduce` accepts an optional second argument, which will be used
as an initial value in the first function call. If the iterable is
empty, the initial value is returned.
Example::
>>> import pykka
>>> f = pykka.ThreadingFuture()
>>> g = f.reduce(lambda x, y: x + y)
>>> f.set(['a', 'b', 'c'])
>>> g.get()
'abc'
>>> f = pykka.ThreadingFuture()
>>> g = f.reduce(lambda x, y: x + y)
>>> f.set([1, 2, 3])
>>> (1 + 2) + 3
6
>>> g.get()
6
>>> f = pykka.ThreadingFuture()
>>> g = f.reduce(lambda x, y: x + y, 5)
>>> f.set([1, 2, 3])
>>> ((5 + 1) + 2) + 3
11
>>> g.get()
11
>>> f = pykka.ThreadingFuture()
>>> g = f.reduce(lambda x, y: x + y, 5)
>>> f.set([])
>>> g.get()
5
.. versionadded:: 1.2
"""
future = self.__class__()
future.set_get_hook(
lambda timeout: functools.reduce(func, self.get(timeout), *args)
)
return future
__await__ = _compat.await_dunder_future
__iter__ = __await__
[docs]def get_all(futures, timeout=None):
"""
Collect all values encapsulated in the list of futures.
If ``timeout`` is not :class:`None`, the method will wait for a reply for
``timeout`` seconds, and then raise :exc:`pykka.Timeout`.
:param futures: futures for the results to collect
:type futures: list of :class:`pykka.Future`
:param timeout: seconds to wait before timeout
:type timeout: float or :class:`None`
:raise: :exc:`pykka.Timeout` if timeout is reached
:returns: list of results
"""
return [future.get(timeout=timeout) for future in futures]