[Tornado AsyncHTTPClient - No Web Server] #python #pipenv #tornado #async #concurrency #httpclient #asynchttpclient #tox #ini #basicauth #auth

README.md

Set-up the environment:

See this gist for more information on Pipenv.

• pipenv --python 3.7
• pipenv shell
• pipenv install tornado==5.0.2
• pipenv install --dev mypy tox flake8

$ cat Pipfile

[[source]]
url = "https://pypi.org/simple"
verify_ssl = true
name = "pypi"

[dev-packages]
mypy = "*"
tox = "*"
"flake8" = "*"

[packages]
tornado = "==5.0.2"

[requires]
python_version = "3.7"

service 1.py

"""
simplest implementation
"""

from tornado.httpclient import AsyncHTTPClient
from tornado.ioloop import IOLoop

AsyncHTTPClient.configure(None, defaults=dict(user_agent="MyUserAgent"))
http_client = AsyncHTTPClient()

async def do_thing():
    response = await http_client.fetch("https://www.integralist.co.uk")
    print(response.code)
    print(response.headers)
    print(response.body)

io_loop = IOLoop.current()
io_loop.run_sync(do_thing)

service 2.py

"""
demonstrates the 'callback' variation of AsyncHTTPClient#fetch
"""

import json

from tornado.httpclient import AsyncHTTPClient
from tornado.ioloop import IOLoop

# if None, then use tornado.simple_httpclient.SimpleAsyncHTTPClient
# otherwise specify alternative client such as curl:
# configure.("tornado.curl_httpclient.CurlAsyncHTTPClient")
AsyncHTTPClient.configure(None, defaults=dict(user_agent="MyUserAgent"))
http_client = AsyncHTTPClient()


def handle_response(response):
    if response.error:
        print("Error: %s" % response.error)
    else:
        print('\n' + str(response.body) + '\n')  # .body is a byte array
        data = json.loads(response.body)
        print(data)


async def get_content():
    await http_client.fetch("http://httpbin.org/json", handle_response)
    
    # Note:
    #
    # The above callback 'style' is different to...
    #
    # response = await http_client.fetch("http://httpbin.org/json")
    # print(response.body)
    #
    # ...which forces the function to wait for the response, then print it,
    # before returning to `main()` which attempts to print its own message.
    #
    # By using the callback style we end up letting `get_content` return immediately. 
    #
    # This isn't to say that the non-callback style is synchronous, it is still asynchronous.
    # In that other processes can be executed while it's happening, but it doesn't work quite the same.
    # As you can see here in this example.
    
    post_data = {"data": "test data"}
    body = urllib.parse.urlencode(post_data)
    response = await http_client.fetch("http://httpbin.org/post", method='POST', headers=None, body=body)
    print('\n' + str(response.body) + '\n')  # .body is a byte array
    
    # As per the tornado documentation:
    # http://www.tornadoweb.org/en/stable/httpclient.html#tornado.httpclient.HTTPRequest
    #
    # The AsyncHTTPClient can accept any keyword args that are supported by 
    # the `HTTPRequest` object, and so if you need to provide basic auth credentials...
    #
    # http_client.fetch(uri, auth_username=<...>, auth_password=<...>)


async def main():
    await get_content()
    print("I won't wait for get_content to finish. I'll show immediately.")

if __name__ == "__main__":
    io_loop = IOLoop.current()
    io_loop.run_sync(main)  # only runs the specified function, then stops
                            # alternatively use IOLoop.current().start()
                            # as that won't stop until explicitly called with
                            # IOLoop.current().stop()

# Other useful ioloop functions:
#
# tornado.ioloop.IOLoop.add_callback
# tornado.ioloop.IOLoop.add_future
# tornado.ioloop.IOLoop.spawn_callback
# tornado.ioloop.PeriodicCallback(task, 1000).start()

# Tornado examples:
#
# https://gist.github.com/lbolla/3826189
# https://github.com/tornadoweb/tornado/blob/master/demos/webspider/webspider.py

tox.ini

[pytest]
# norecursedirs = lib
addopts = -p no:cacheprovider

[flake8]
max_line_length = 120
exclude = lib,node_modules
ignore = E116
# https://pep8.readthedocs.io/en/latest/intro.html#error-codes