| commit | author | age | ||
| b731b5 | 1 | .. _qtut_hello_world: |
| PE | 2 | |
| b1b922 | 3 | ================================ |
| PE | 4 | 01: Single-File Web Applications |
| 5 | ================================ | |
| 6 | ||
| 878d1a | 7 | What's the simplest way to get started in Pyramid? A single-file module. No |
| SP | 8 | Python packages, no ``pip install -e .``, no other machinery. |
| 9 | ||
| b1b922 | 10 | |
| PE | 11 | Background |
| 12 | ========== | |
| 13 | ||
| 99d45a | 14 | Microframeworks were all the rage, until the next shiny thing came along. "Microframework" is a marketing |
| 878d1a | 15 | term, not a technical one. They have a low mental overhead: they do so little, |
| SP | 16 | the only things you have to worry about are *your things*. |
| b1b922 | 17 | |
| 878d1a | 18 | Pyramid is special because it can act as a single-file module microframework. |
| SP | 19 | You can have a single Python file that can be executed directly by Python. But |
| 20 | Pyramid also provides facilities to scale to the largest of applications. | |
| b1b922 | 21 | |
| 878d1a | 22 | Python has a standard called :term:`WSGI` that defines how Python web |
| SP | 23 | applications plug into standard servers, getting passed incoming requests, and |
| 24 | returning responses. Most modern Python web frameworks obey an "MVC" | |
| 25 | (model-view-controller) application pattern, where the data in the model has a | |
| 26 | view that mediates interaction with outside systems. | |
| b1b922 | 27 | |
| 878d1a | 28 | In this step we'll see a brief glimpse of WSGI servers, WSGI applications, |
| SP | 29 | requests, responses, and views. |
| 30 | ||
| b1b922 | 31 | |
| PE | 32 | Objectives |
| 33 | ========== | |
| 34 | ||
| 878d1a | 35 | - Get a running Pyramid web application, as simply as possible. |
| b1b922 | 36 | |
| 878d1a | 37 | - Use that as a well-understood base for adding each unit of complexity. |
| b1b922 | 38 | |
| 878d1a | 39 | - Initial exposure to WSGI apps, requests, views, and responses. |
| SP | 40 | |
| b1b922 | 41 | |
| PE | 42 | Steps |
| 43 | ===== | |
| 44 | ||
| 187104 | 45 | #. Make sure you have followed the steps in :doc:`requirements`. |
| b1b922 | 46 | |
| 34e974 | 47 | #. Starting from your workspace directory |
| PE | 48 | (``~/projects/quick_tutorial``), create a directory for this step: |
| b1b922 | 49 | |
| PE | 50 | .. code-block:: bash |
| 51 | ||
| 99d45a | 52 | $ cd ~/projects/quick_tutorial; mkdir hello_world; cd hello_world |
| b1b922 | 53 | |
| PE | 54 | #. Copy the following into ``hello_world/app.py``: |
| 55 | ||
| 56 | .. literalinclude:: hello_world/app.py | |
| 57 | :linenos: | |
| 58 | ||
| 59 | #. Run the application: | |
| 60 | ||
| 61 | .. code-block:: bash | |
| 62 | ||
| 187104 | 63 | $ $VENV/bin/python app.py |
| b1b922 | 64 | |
| d749bf | 65 | #. Open http://localhost:6543/ in your browser. |
| b1b922 | 66 | |
| 878d1a | 67 | |
| b1b922 | 68 | Analysis |
| PE | 69 | ======== |
| 70 | ||
| 878d1a | 71 | New to Python web programming? If so, some lines in the module merit |
| b1b922 | 72 | explanation: |
| PE | 73 | |
| 878d1a | 74 | #. *Line 11*. The ``if __name__ == '__main__':`` is Python's way of saying, |
| SP | 75 | "Start here when running from the command line", rather than when this |
| 76 | module is imported. | |
| b1b922 | 77 | |
| d91e5d | 78 | #. *Lines 12-14*. Use Pyramid's :term:`configurator` in a :term:`context manager` to connect :term:`view` |
| 878d1a | 79 | code to a particular URL :term:`route`. |
| b1b922 | 80 | |
| 878d1a | 81 | #. *Lines 6-8*. Implement the view code that generates the :term:`response`. |
| b1b922 | 82 | |
| 878d1a | 83 | #. *Lines 15-17*. Publish a :term:`WSGI` app using an HTTP server. |
| b1b922 | 84 | |
| 878d1a | 85 | As shown in this example, the :term:`configurator` plays a central role in |
| SP | 86 | Pyramid development. Building an application from loosely-coupled parts via |
| 87 | :ref:`configuration_narr` is a central idea in Pyramid, one that we will | |
| 88 | revisit regularly in this *Quick Tutorial*. | |
| 89 | ||
| b1b922 | 90 | |
| 65687f | 91 | Extra credit |
| b1b922 | 92 | ============ |
| PE | 93 | |
| 94 | #. Why do we do this: | |
| 95 | ||
| 96 | .. code-block:: python | |
| 97 | ||
| 92b27d | 98 | print('Incoming request') |
| b1b922 | 99 | |
| PE | 100 | ...instead of: |
| 101 | ||
| 102 | .. code-block:: python | |
| 103 | ||
| 92b27d | 104 | print 'Incoming request' |
| b1b922 | 105 | |
| PE | 106 | #. What happens if you return a string of HTML? A sequence of integers? |
| 107 | ||
| 878d1a | 108 | #. Put something invalid, such as ``print xyz``, in the view function. Kill |
| SP | 109 | your ``python app.py`` with ``ctrl-C`` and restart, then reload your |
| 110 | browser. See the exception in the console? | |
| b1b922 | 111 | |
| 878d1a | 112 | #. The ``GI`` in ``WSGI`` stands for "Gateway Interface". What web standard is |
| SP | 113 | this modelled after? |
