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import collections.abc
import logging
from typing import (
Iterable,
AsyncIterator,
TypeVar,
Callable,
Tuple,
Optional,
Awaitable,
)
_LOGGER = logging.getLogger(__name__)
ReturnType = TypeVar("ReturnType")
ResponseType = TypeVar("ResponseType")
__all__ = [
"AsyncPageIterator",
"AsyncItemPaged"
]
class AsyncList(AsyncIterator[ReturnType]):
def __init__(self, iterable: Iterable[ReturnType]) -> None:
"""Change an iterable into a fake async iterator.
Coul be useful to fill the async iterator contract when you get a list.
:param iterable: A sync iterable of T
"""
# Technically, if it's a real iterator, I don't need "iter"
# but that will cover iterable and list as well with no troubles created.
self._iterator = iter(iterable)
async def __anext__(self) -> ReturnType:
try:
return next(self._iterator)
except StopIteration as err:
raise StopAsyncIteration() from err
[docs]class AsyncPageIterator(AsyncIterator[AsyncIterator[ReturnType]]):
def __init__(
self,
get_next: Callable[
[Optional[str]], Awaitable[ResponseType]
],
extract_data: Callable[
[ResponseType], Awaitable[Tuple[str, AsyncIterator[ReturnType]]]
],
continuation_token: Optional[str] = None,
) -> None:
"""Return an async iterator of pages.
:param get_next: Callable that take the continuation token and return a HTTP response
:param extract_data: Callable that take an HTTP response and return a tuple continuation token,
list of ReturnType
:param str continuation_token: The continuation token needed by get_next
"""
self._get_next = get_next
self._extract_data = extract_data
self.continuation_token = continuation_token
self._did_a_call_already = False
self._response = None
self._current_page = None
async def __anext__(self):
if self.continuation_token is None and self._did_a_call_already:
raise StopAsyncIteration("End of paging")
self._response = await self._get_next(self.continuation_token)
self._did_a_call_already = True
self.continuation_token, self._current_page = await self._extract_data(
self._response
)
# If current_page was a sync list, wrap it async-like
if isinstance(self._current_page, collections.abc.Iterable):
self._current_page = AsyncList(self._current_page)
return self._current_page
[docs]class AsyncItemPaged(AsyncIterator[ReturnType]):
def __init__(self, *args, **kwargs) -> None:
"""Return an async iterator of items.
args and kwargs will be passed to the AsyncPageIterator constructor directly,
except page_iterator_class
"""
self._args = args
self._kwargs = kwargs
self._page_iterator = (
None
) # type: Optional[AsyncIterator[AsyncIterator[ReturnType]]]
self._page = None # type: Optional[AsyncIterator[ReturnType]]
self._page_iterator_class = self._kwargs.pop(
"page_iterator_class", AsyncPageIterator
)
[docs] def by_page(
self,
continuation_token: Optional[str] = None,
) -> AsyncIterator[AsyncIterator[ReturnType]]:
"""Get an async iterator of pages of objects, instead of an async iterator of objects.
:param str continuation_token:
An opaque continuation token. This value can be retrieved from the
continuation_token field of a previous generator object. If specified,
this generator will begin returning results from this point.
:returns: An async iterator of pages (themselves async iterator of objects)
"""
return self._page_iterator_class(
*self._args, **self._kwargs, continuation_token=continuation_token
)
async def __anext__(self) -> ReturnType:
if self._page_iterator is None:
self._page_iterator = self.by_page()
return await self.__anext__()
if self._page is None:
# Let it raise StopAsyncIteration
self._page = await self._page_iterator.__anext__()
return await self.__anext__()
try:
return await self._page.__anext__()
except StopAsyncIteration:
self._page = None
return await self.__anext__()