HTTP Client¶
Make a Request¶
Begin by importing the aiohttp module:
import aiohttp
Now, let’s try to get a web-page. For example let’s get GitHub’s public time-line
with aiohttp.ClientSession() as session:
async with session.get('https://api.github.com/events') as resp:
print(resp.status)
print(await resp.text())
Now, we have a ClientSession
called session
and
a ClientResponse
object called resp
. We can get all the
information we need from the response. The mandatory parameter of
ClientSession.get()
coroutine is an HTTP url.
In order to make an HTTP POST request use ClientSession.post()
coroutine:
session.post('http://httpbin.org/post', data=b'data')
Other HTTP methods are available as well:
session.put('http://httpbin.org/put', data=b'data')
session.delete('http://httpbin.org/delete')
session.head('http://httpbin.org/get')
session.options('http://httpbin.org/get')
session.patch('http://httpbin.org/patch', data=b'data')
Passing Parameters In URLs¶
You often want to send some sort of data in the URL’s query string. If
you were constructing the URL by hand, this data would be given as key/value
pairs in the URL after a question mark, e.g. httpbin.org/get?key=val
.
Requests allows you to provide these arguments as a dict
, using the
params
keyword argument. As an example, if you wanted to pass
key1=value1
and key2=value2
to httpbin.org/get
, you would use the
following code:
params = {'key1': 'value1', 'key2': 'value2'}
async with session.get('http://httpbin.org/get',
params=params) as resp:
assert resp.url == 'http://httpbin.org/get?key2=value2&key1=value1'
You can see that the URL has been correctly encoded by printing the URL.
For sending data with multiple values for the same key
MultiDict
may be used as well.
It is also possible to pass a list of 2 item tuples as parameters, in that case you can specify multiple values for each key:
params = [('key', 'value1'), ('key', 'value2')]
async with session.get('http://httpbin.org/get',
params=params) as r:
assert r.url == 'http://httpbin.org/get?key=value2&key=value1'
You can also pass str
content as param, but beware - content
is not encoded by library. Note that +
is not encoded:
async with session.get('http://httpbin.org/get',
params='key=value+1') as r:
assert r.url = 'http://httpbin.org/get?key=value+1'
Response Content¶
We can read the content of the server’s response. Consider the GitHub time-line again:
async with session.get('https://api.github.com/events') as resp:
print(await resp.text())
will printout something like:
'[{"created_at":"2015-06-12T14:06:22Z","public":true,"actor":{...
aiohttp
will automatically decode the content from the server. You can
specify custom encoding for the text()
method:
await resp.text(encoding='windows-1251')
Binary Response Content¶
You can also access the response body as bytes, for non-text requests:
print(await resp.read())
b'[{"created_at":"2015-06-12T14:06:22Z","public":true,"actor":{...
The gzip
and deflate
transfer-encodings are automatically
decoded for you.
JSON Response Content¶
There’s also a built-in JSON decoder, in case you’re dealing with JSON data:
async with session.get('https://api.github.com/events') as resp:
print(await resp.json())
In case that JSON decoding fails, json()
will
raise an exception. It is possible to specify custom encoding and
decoder functions for the json()
call.
Streaming Response Content¶
While methods read()
,
json()
and text()
are very
convenient you should use them carefully. All these methods load the
whole response in memory. For example if you want to download several
gigabyte sized files, these methods will load all the data in
memory. Instead you can use the content
attribute. It is an instance of the aiohttp.StreamReader
class. The gzip
and deflate
transfer-encodings are
automatically decoded for you:
async with session.get('https://api.github.com/events') as resp:
await resp.content.read(10)
In general, however, you should use a pattern like this to save what is being streamed to a file:
with open(filename, 'wb') as fd:
while True:
chunk = await resp.content.read(chunk_size)
if not chunk:
break
fd.write(chunk)
It is not possible to use read()
,
json()
and text()
after
explicit reading from content
.
Releasing Response¶
Don’t forget to release response after use. This will ensure explicit behavior and proper connection pooling.
The easiest way to correctly response releasing is async with
statement:
async with session.get(url) as resp:
pass
But explicit release()
call also may be used:
await resp.release()
But it’s not necessary if you use read()
,
json()
and text()
methods.
They do release connection internally but better don’t rely on that
behavior.
Custom Headers¶
If you need to add HTTP headers to a request, pass them in a
dict
to the headers parameter.
For example, if you want to specify the content-type for the previous example:
import json
url = 'https://api.github.com/some/endpoint'
payload = {'some': 'data'}
headers = {'content-type': 'application/json'}
await session.post(url,
data=json.dumps(payload),
headers=headers)
Custom Cookies¶
To send your own cookies to the server, you can use the cookies parameter:
url = 'http://httpbin.org/cookies'
cookies = dict(cookies_are='working')
async with session.get(url, cookies=cookies) as resp:
assert await resp.json() == {"cookies":
{"cookies_are": "working"}}
More complicated POST requests¶
Typically, you want to send some form-encoded data — much like an HTML form. To do this, simply pass a dictionary to the data argument. Your dictionary of data will automatically be form-encoded when the request is made:
payload = {'key1': 'value1', 'key2': 'value2'}
async with session.post('http://httpbin.org/post',
data=payload) as resp:
print(await resp.text())
{
...
"form": {
"key2": "value2",
"key1": "value1"
},
...
}
If you want to send data that is not form-encoded you can do it by
passing a str
instead of a dict
. This data will be
posted directly.
For example, the GitHub API v3 accepts JSON-Encoded POST/PATCH data:
import json
url = 'https://api.github.com/some/endpoint'
payload = {'some': 'data'}
async with session.post(url, data=json.dumps(payload)) as resp:
...
POST a Multipart-Encoded File¶
To upload Multipart-encoded files:
url = 'http://httpbin.org/post'
files = {'file': open('report.xls', 'rb')}
await session.post(url, data=files)
You can set the filename, content_type explicitly:
url = 'http://httpbin.org/post'
data = FormData()
data.add_field('file',
open('report.xls', 'rb'),
filename='report.xls',
content_type='application/vnd.ms-excel')
await session.post(url, data=data)
If you pass a file object as data parameter, aiohttp will stream it to
the server automatically. Check StreamReader
for supported format information.
See also
Streaming uploads¶
aiohttp
supports multiple types of streaming uploads, which allows you to
send large files without reading them into memory.
As a simple case, simply provide a file-like object for your body:
with open('massive-body', 'rb') as f:
await session.post('http://some.url/streamed', data=f)
Or you can provide an coroutine that yields bytes objects:
@asyncio.coroutine
def my_coroutine():
chunk = yield from read_some_data_from_somewhere()
if not chunk:
return
yield chunk
Warning
yield
expression is forbidden inside async def
.
Note
It is not a standard coroutine as it yields values so it
can not be used like yield from my_coroutine()
.
aiohttp
internally handles such coroutines.
Also it is possible to use a StreamReader
object. Lets say we want to upload a file from another request and
calculate the file SHA1 hash:
async def feed_stream(resp, stream):
h = hashlib.sha256()
while True:
chunk = await resp.content.readany()
if not chunk:
break
h.update(chunk)
s.feed_data(chunk)
return h.hexdigest()
resp = session.get('http://httpbin.org/post')
stream = StreamReader()
loop.create_task(session.post('http://httpbin.org/post', data=stream))
file_hash = await feed_stream(resp, stream)
Because the response content attribute is a
StreamReader
, you can chain get and post
requests together (aka HTTP pipelining):
r = await session.get, 'http://python.org')
await session.post('http://httpbin.org/post',
data=r.content)
Uploading pre-compressed data¶
To upload data that is already compressed before passing it to aiohttp, call
the request function with compress=False
and set the used compression
algorithm name (usually deflate or zlib) as the value of the
Content-Encoding
header:
async def my_coroutine(session, headers, my_data):
data = zlib.compress(my_data)
headers = {'Content-Encoding': 'deflate'}
async with session.post('http://httpbin.org/post',
data=data,
headers=headers,
compress=False):
pass
Keep-Alive, connection pooling and cookie sharing¶
ClientSession
may be used for sharing cookies
between multiple requests:
session = aiohttp.ClientSession()
await session.post(
'http://httpbin.org/cookies/set/my_cookie/my_value')
async with session.get('http://httpbin.org/cookies') as r:
json = await r.json()
assert json['cookies']['my_cookie'] == 'my_value'
You also can set default headers for all session requests:
session = aiohttp.ClientSession(
headers={"Authorization": "Basic bG9naW46cGFzcw=="})
async with s.get("http://httpbin.org/headers") as r:
json = yield from r.json()
assert json['headers']['Authorization'] == 'Basic bG9naW46cGFzcw=='
ClientSession
supports keep-alive requests
and connection pooling out-of-the-box.
Connectors¶
To tweak or change transport layer of requests you can pass a custom
connector to ClientSession
and family. For example:
conn = aiohttp.TCPConnector()
session = aiohttp.ClientSession(connector=aiohttp.TCPConnector())
See also
Connectors section for more information about different connector types and configuration options.
Limiting connection pool size¶
To limit amount of simultaneously opened connection to the same
endpoint ((host, port, is_ssl)
triple) you can pass limit
parameter to connector:
conn = aiohttp.TCPConnector(limit=30)
The example limits amount of parallel connections to 30.
SSL control for TCP sockets¶
TCPConnector
constructor accepts mutually
exclusive verify_ssl and ssl_context params.
By default it uses strict checks for HTTPS protocol. Certification
checks can be relaxed by passing verify_ssl=False
:
conn = aiohttp.TCPConnector(verify_ssl=False)
session = aiohttp.ClientSession(connector=conn)
r = await session.get('https://example.com')
If you need to setup custom ssl parameters (use own certification
files for example) you can create a ssl.SSLContext
instance and
pass it into the connector:
sslcontext = ssl.create_default_context(cafile='/path/to/ca-bundle.crt')
conn = aiohttp.TCPConnector(ssl_context=sslcontext)
session = aiohttp.ClientSession(connector=conn)
r = await session.get('https://example.com')
You may also verify certificates via MD5, SHA1, or SHA256 fingerprint:
# Attempt to connect to https://www.python.org
# with a pin to a bogus certificate:
bad_md5 = b'\xa2\x06G\xad\xaa\xf5\xd8\\J\x99^by;\x06='
conn = aiohttp.TCPConnector(fingerprint=bad_md5)
session = aiohttp.ClientSession(connector=conn)
exc = None
try:
r = yield from session.get('https://www.python.org')
except FingerprintMismatch as e:
exc = e
assert exc is not None
assert exc.expected == bad_md5
# www.python.org cert's actual md5
assert exc.got == b'\xca;I\x9cuv\x8es\x138N$?\x15\xca\xcb'
Note that this is the fingerprint of the DER-encoded certificate.
If you have the certificate in PEM format, you can convert it to
DER with e.g. openssl x509 -in crt.pem -inform PEM -outform DER > crt.der
.
Tip: to convert from a hexadecimal digest to a binary byte-string, you can use
binascii.unhexlify
:
md5_hex = 'ca3b499c75768e7313384e243f15cacb'
from binascii import unhexlify
assert unhexlify(md5_hex) == b'\xca;I\x9cuv\x8es\x138N$?\x15\xca\xcb'
Unix domain sockets¶
If your HTTP server uses UNIX domain sockets you can use
UnixConnector
:
conn = aiohttp.UnixConnector(path='/path/to/socket')
session = aiohttp.ClientSession(connector=conn)
Proxy support¶
aiohttp supports proxy. You have to use
ProxyConnector
:
conn = aiohttp.ProxyConnector(proxy="http://some.proxy.com")
session = aiohttp.ClientSession(connector=conn)
async with session.get('http://python.org') as resp:
print(resp.status)
ProxyConnector
also supports proxy authorization:
conn = aiohttp.ProxyConnector(
proxy="http://some.proxy.com",
proxy_auth=aiohttp.BasicAuth('user', 'pass'))
session = aiohttp.ClientSession(connector=conn)
async with session.get('http://python.org') as r:
assert r.status == 200
Authentication credentials can be passed in proxy URL:
conn = aiohttp.ProxyConnector(
proxy="http://user:pass@some.proxy.com")
Response Status Codes¶
We can check the response status code:
async with session.get('http://httpbin.org/get') as resp:
assert resp.status == 200
Response Headers¶
We can view the server’s response ClientResponse.headers
using
a CIMultiDictProxy
:
>>> resp.headers
{'ACCESS-CONTROL-ALLOW-ORIGIN': '*',
'CONTENT-TYPE': 'application/json',
'DATE': 'Tue, 15 Jul 2014 16:49:51 GMT',
'SERVER': 'gunicorn/18.0',
'CONTENT-LENGTH': '331',
'CONNECTION': 'keep-alive'}
The dictionary is special, though: it’s made just for HTTP headers. According to RFC 7230, HTTP Header names are case-insensitive. It also supports multiple values for the same key as HTTP protocol does.
So, we can access the headers using any capitalization we want:
>>> resp.headers['Content-Type']
'application/json'
>>> resp.headers.get('content-type')
'application/json'
All headers converted from binary data using UTF-8 with
surrogateescape
option. That works fine on most cases but
sometimes unconverted data is needed if a server uses nonstandard
encoding. While these headers are malformed from RFC 7230
perspective they are may be retrieved by using
ClientResponse.raw_headers
property:
>>> resp.raw_headers
((b'SERVER', b'nginx'),
(b'DATE', b'Sat, 09 Jan 2016 20:28:40 GMT'),
(b'CONTENT-TYPE', b'text/html; charset=utf-8'),
(b'CONTENT-LENGTH', b'12150'),
(b'CONNECTION', b'keep-alive'))
Response Cookies¶
If a response contains some Cookies, you can quickly access them:
url = 'http://example.com/some/cookie/setting/url'
async with session.get(url) as resp:
print(resp.cookies['example_cookie_name'])
Note
Response cookies contain only values, that were in Set-Cookie
headers
of the last request in redirection chain. To gather cookies between all
redirection requests you can use aiohttp.ClientSession object.
Response History¶
If a request was redirected, it is possible to view previous responses using
the history
attribute:
>>> resp = await session.get('http://example.com/some/redirect/')
>>> resp
<ClientResponse(http://example.com/some/other/url/) [200]>
>>> resp.history
(<ClientResponse(http://example.com/some/redirect/) [301]>,)
If no redirects occurred or allow_redirects
is set to False
,
history will be an empty sequence.
WebSockets¶
New in version 0.15.
aiohttp
works with client websockets out-of-the-box.
You have to use the aiohttp.ClientSession.ws_connect()
coroutine
for client websocket connection. It accepts a url as a first
parameter and returns ClientWebSocketResponse
, with that
object you can communicate with websocket server using response’s
methods:
session = aiohttp.ClientSession()
async with session.ws_connect('http://example.org/websocket') as ws:
async for msg in ws:
if msg.tp == aiohttp.MsgType.text:
if msg.data == 'close cmd':
await ws.close()
break
else:
ws.send_str(msg.data + '/answer')
elif msg.tp == aiohttp.MsgType.closed:
break
elif msg.tp == aiohttp.MsgType.error:
break
You must use the only websocket task for both reading (e.g await
ws.receive()
or async for msg in ws:
) and writing but may have
multiple writer tasks which can only send data asynchronously (by
ws.send_str('data')
for example).
Timeouts¶
The example wraps a client call in Timeout
context
manager, adding timeout for both connecting and response body
reading procedures:
with aiohttp.Timeout(0.001):
async with aiohttp.get('https://github.com') as r:
await r.text()