Streaming API¶
aiohttp
uses streams for retrieving BODIES:
aiohttp.web.Request.content
and
aiohttp.ClientResponse.content
are properties with stream API.
-
class
aiohttp.
StreamReader
¶ The reader from incoming stream.
User should never instantiate streams manually but use existing
aiohttp.web.Request.content
andaiohttp.ClientResponse.content
properties for accessing raw BODY data.
Reading Methods¶
-
coroutine
StreamReader.
read
(n=-1)¶ Read up to n bytes. If n is not provided, or set to
-1
, read until EOF and return all read bytes.If the EOF was received and the internal buffer is empty, return an empty bytes object.
Parameters: n (int) – how many bytes to read, -1
for the whole stream.Return bytes: the given data
-
coroutine
StreamReader.
readany
()¶ Read next data portion for the stream.
Returns immediately if internal buffer has a data.
Return bytes: the given data
-
coroutine
StreamReader.
readexactly
(n)¶ Read exactly n bytes.
Raise an
asyncio.IncompleteReadError
if the end of the stream is reached before n can be read, theasyncio.IncompleteReadError.partial
attribute of the exception contains the partial read bytes.Parameters: n (int) – how many bytes to read. Return bytes: the given data
-
coroutine
StreamReader.
readline
()¶ Read one line, where “line” is a sequence of bytes ending with
\n
.If EOF is received, and
\n
was not found, the method will return the partial read bytes.If the EOF was received and the internal buffer is empty, return an empty bytes object.
Return bytes: the given line
-
coroutine
StreamReader.
readchunk
()¶ Read a chunk of data as it was received by the server.
Returns a tuple of (data, end_of_HTTP_chunk).
When chunked transfer encoding is used, end_of_HTTP_chunk is a
bool
indicating if the end of the data corresponds to the end of a HTTP chunk, otherwise it is alwaysFalse
.Return tuple[bytes, bool]: a chunk of data and a bool
that isTrue
when the end of the returned chunk corresponds to the end of a HTTP chunk.
Asynchronous Iteration Support¶
Stream reader supports asynchronous iteration over BODY.
By default it iterates over lines:
async for line in response.content:
print(line)
Also there are methods for iterating over data chunks with maximum size limit and over any available data.
-
async-for
StreamReader.
iter_chunked
(n)¶ Iterates over data chunks with maximum size limit:
async for data in response.content.iter_chunked(1024): print(data)
-
async-for
StreamReader.
iter_any
()¶ Iterates over data chunks in order of intaking them into the stream:
async for data in response.content.iter_any(): print(data)
-
async-for
StreamReader.
iter_chunks
()¶ Iterates over data chunks as received from the server:
async for data, _ in response.content.iter_chunks(): print(data)
If chunked transfer encoding is used, the original http chunks formatting can be retrieved by reading the second element of returned tuples:
buffer = b"" async for data, end_of_http_chunk in response.content.iter_chunks(): buffer += data if end_of_http_chunk: print(buffer) buffer = b""
Helpers¶
-
StreamReader.
exception
()¶ Get the exception occurred on data reading.
-
aiohttp.
is_eof
()¶ Return
True
if EOF was reached.Internal buffer may be not empty at the moment.
See also
-
StreamReader.
at_eof
()¶ Return
True
if the buffer is empty and EOF was reached.
-
StreamReader.
read_nowait
(n=None)¶ Returns data from internal buffer if any, empty bytes object otherwise.
Raises
RuntimeError
if other coroutine is waiting for stream.Parameters: n (int) – how many bytes to read, -1
for the whole internal buffer.Return bytes: the given data
-
StreamReader.
unread_data
(data)¶ Rollback reading some data from stream, inserting it to buffer head.
Parameters: data (bytes) – data to push back into the stream.
-
coroutine
aiohttp.
wait_eof
()¶ Wait for EOF. The given data may be accessible by upcoming read calls.