Source code for azure.core.async_paging

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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__()