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158 lines
5.5 KiB
Markdown
[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (How to write a Python web API with Pyramid and Cornice)
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[#]: via: (https://opensource.com/article/20/1/python-web-api-pyramid-cornice)
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[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
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How to write a Python web API with Pyramid and Cornice
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======
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Use Pyramid and Cornice to build and document scalable RESTful web
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services.
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![Searching for code][1]
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[Python][2] is a high-level, object-oriented programming language known for its simple syntax. It is consistently among the top-rated programming languages for building RESTful APIs.
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[Pyramid][3] is a Python web framework designed to scale up with an application: it's simple for simple applications but can grow for big, complex applications. Among other things, Pyramid powers PyPI, the Python package index. [Cornice][4] provides helpers to build and document REST-ish web services with Pyramid.
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This article will use the example of a web service to get famous quotes to show how to use these tools.
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### Set up a Pyramid application
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Start by creating a virtual environment for your application and a file to hold the code:
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```
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$ mkdir tutorial
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$ cd tutorial
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$ touch main.py
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$ python3 -m venv env
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$ source env/bin/activate
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(env) $ pip3 install cornice twisted
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```
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### Import the Cornice and Pyramid modules
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Import these modules with:
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```
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from pyramid.config import Configurator
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from cornice import Service
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```
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### Define the service
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Define the quotes service as a **Service** object:
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```
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QUOTES = Service(name='quotes',
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path='/',
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description='Get quotes')
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```
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### Write the quotes logic
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So far, this only supports **GET**ing quotes. Decorate the function with **QUOTES.get**; this is how you can tie in the logic to the REST service:
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```
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@QUOTES.get()
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def get_quote(request):
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return {
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'William Shakespeare': {
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'quote': ['Love all, trust a few, do wrong to none',
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'Some are born great, some achieve greatness, and some have greatness thrust upon them.']
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},
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'Linus': {
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'quote': ['Talk is cheap. Show me the code.']
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}
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}
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```
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Note that unlike in other frameworks, the **get_quote** function is _not_ changed by the decorator. If you import this module, you can still call the function regularly and inspect the result.
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This is useful when writing unit tests for Pyramid RESTful services.
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### Define the application object
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Finally, use **scan** to find all decorated functions and add them to the configuration:
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```
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with Configurator() as config:
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config.include("cornice")
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config.scan()
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application = config.make_wsgi_app()
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```
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The default for scan is to scan the current module. You can also give the name of a package if you want to scan all modules in a package.
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### Run the service
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I use Twisted's WSGI server to run the application, but you can use any other [WSGI][5] server, like Gunicorn or uWSGI, if you want:
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```
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`(env)$ python -m twisted web --wsgi=main.application`
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```
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By default, Twisted's WSGI server runs on port 8080. You can test the service with [HTTPie][6]:
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```
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(env) $ pip install httpie
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...
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(env) $ http GET <http://localhost:8080/>
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HTTP/1.1 200 OK
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Content-Length: 220
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Content-Type: application/json
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Date: Mon, 02 Dec 2019 16:49:27 GMT
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Server: TwistedWeb/19.10.0
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X-Content-Type-Options: nosniff
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{
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"Linus": {
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"quote": [
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"Talk is cheap. Show me the code."
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]
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},
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"William Shakespeare": {
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"quote": [
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"Love all,trust a few,do wrong to none",
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"Some are born great, some achieve greatness, and some greatness thrust upon them."
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]
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}
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}
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```
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### Why use Pyramid?
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Pyramid is not the most popular framework, but it is used in some high-profile projects like [PyPI][7]. I like Pyramid because it is one of the frameworks that took unit testing seriously: because the decorators do not modify the function and there are no thread-local variables, functions are callable directly from unit tests. For example, functions that need access to the database will get it from the **request** object passed in via **request.config**. This allows a unit tester to put a mock (or real) database object in the request, instead of carefully setting globals, thread-local variables, or other framework-specific things.
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If you're looking for a well-tested library to build your next API, give Pyramid a try. You won't be disappointed.
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/1/python-web-api-pyramid-cornice
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作者：[Moshe Zadka][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/moshez
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/search_find_code_python_programming.png?itok=ynSL8XRV (Searching for code)
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[2]: https://opensource.com/resources/python
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[3]: https://opensource.com/article/18/5/pyramid-framework
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[4]: https://cornice.readthedocs.io/en/latest/
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[5]: https://en.wikipedia.org/wiki/Web_Server_Gateway_Interface
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[6]: https://opensource.com/article/19/8/getting-started-httpie
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[7]: https://pypi.org/
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