1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
|
=========================
Defining the Domain Model
=========================
The first change we'll make to our stock ``pcreate``-generated application will
be to define a wiki page :term:`domain model`.
We'll do this inside our ``mymodel.py`` file.
Edit ``mymodel.py``
-------------------
.. note::
There is nothing special about the filename ``mymodel.py`` except that it
is a Python module. A project may have many models throughout its codebase
in arbitrarily named modules. Modules implementing models often have
``model`` in their names or they may live in a Python subpackage of your
application package named ``models`` (as we've done in this tutorial), but
this is only a convention and not a requirement.
Open the ``tutorial/models/mymodel.py`` file and edit it to look like
the following:
.. literalinclude:: src/models/tutorial/models/mymodel.py
:linenos:
:language: py
:emphasize-lines: 10-12,14-15
The highlighted lines are the ones that need to be changed, as well as
removing lines that reference ``Index``.
The first thing we've done is remove the stock ``MyModel`` class
from the generated ``models.py`` file. The ``MyModel`` class is only a
sample and we're not going to use it.
Then we added a ``Page`` class. Because this is a SQLAlchemy application,
this class inherits from an instance of
:func:`sqlalchemy.ext.declarative.declarative_base`.
.. literalinclude:: src/models/tutorial/models/mymodel.py
:pyobject: Page
:linenos:
:language: python
As you can see, our ``Page`` class has a class-level attribute
``__tablename__`` which equals the string ``'pages'``. This means that
SQLAlchemy will store our wiki data in a SQL table named ``pages``. Our
``Page`` class will also have class-level attributes named ``id``, ``name``,
and ``data`` (all instances of :class:`sqlalchemy.schema.Column`). These will
map to columns in the ``pages`` table. The ``id`` attribute will be the
primary key in the table. The ``name`` attribute will be a text attribute,
each value of which needs to be unique within the column. The ``data``
attribute is a text attribute that will hold the body of each page.
Edit ``models/__init__.py``
---------------------------
Since we are using a package for our models, we also need to update our
``__init__.py`` file to ensure that the model is attached to the metadata.
Open the ``tutorial/models/__init__.py`` file and edit it to look like
the following:
.. literalinclude:: src/models/tutorial/models/__init__.py
:linenos:
:language: py
:emphasize-lines: 8
Here we need to align our import with the name of the model ``Page``.
Edit ``scripts/initializedb.py``
--------------------------------
We haven't looked at the details of this file yet, but within the ``scripts``
directory of your ``tutorial`` package is a file named ``initializedb.py``.
Code in this file is executed whenever we run the ``initialize_tutorial_db``
command, as we did in the installation step of this tutorial.
Since we've changed our model, we need to make changes to our
``initializedb.py`` script. In particular, we'll replace our import of
``MyModel`` with one of ``Page`` and we'll change the very end of the script
to create a ``Page`` rather than a ``MyModel`` and add it to our
``dbsession``.
Open ``tutorial/scripts/initializedb.py`` and edit it to look like
the following:
.. literalinclude:: src/models/tutorial/scripts/initializedb.py
:linenos:
:language: python
:emphasize-lines: 18,44-45
Only the highlighted lines need to be changed.
Installing the project and re-initializing the database
-------------------------------------------------------
Because our model has changed, in order to reinitialize the database, we need
to rerun the ``initialize_tutorial_db`` command to pick up the changes you've
made to both the models.py file and to the initializedb.py file. See
:ref:`initialize_db_wiki2` for instructions.
Success will look something like this::
2016-02-12 01:06:35,855 INFO [sqlalchemy.engine.base.Engine:1192][MainThread] SELECT CAST('test plain returns' AS VARCHAR(60)) AS anon_1
2016-02-12 01:06:35,855 INFO [sqlalchemy.engine.base.Engine:1193][MainThread] ()
2016-02-12 01:06:35,855 INFO [sqlalchemy.engine.base.Engine:1192][MainThread] SELECT CAST('test unicode returns' AS VARCHAR(60)) AS anon_1
2016-02-12 01:06:35,855 INFO [sqlalchemy.engine.base.Engine:1193][MainThread] ()
2016-02-12 01:06:35,856 INFO [sqlalchemy.engine.base.Engine:1097][MainThread] PRAGMA table_info("pages")
2016-02-12 01:06:35,856 INFO [sqlalchemy.engine.base.Engine:1100][MainThread] ()
2016-02-12 01:06:35,856 INFO [sqlalchemy.engine.base.Engine:1097][MainThread] PRAGMA table_info("users")
2016-02-12 01:06:35,856 INFO [sqlalchemy.engine.base.Engine:1100][MainThread] ()
2016-02-12 01:06:35,857 INFO [sqlalchemy.engine.base.Engine:1097][MainThread]
CREATE TABLE users (
id INTEGER NOT NULL,
name TEXT NOT NULL,
role TEXT NOT NULL,
password_hash TEXT,
CONSTRAINT pk_users PRIMARY KEY (id),
CONSTRAINT uq_users_name UNIQUE (name)
)
2016-02-12 01:06:35,857 INFO [sqlalchemy.engine.base.Engine:1100][MainThread] ()
2016-02-12 01:06:35,858 INFO [sqlalchemy.engine.base.Engine:686][MainThread] COMMIT
2016-02-12 01:06:35,858 INFO [sqlalchemy.engine.base.Engine:1097][MainThread]
CREATE TABLE pages (
id INTEGER NOT NULL,
name TEXT NOT NULL,
data INTEGER NOT NULL,
creator_id INTEGER NOT NULL,
CONSTRAINT pk_pages PRIMARY KEY (id),
CONSTRAINT uq_pages_name UNIQUE (name),
CONSTRAINT fk_pages_creator_id_users FOREIGN KEY(creator_id) REFERENCES users (id)
)
2016-02-12 01:06:35,859 INFO [sqlalchemy.engine.base.Engine:1100][MainThread] ()
2016-02-12 01:06:35,859 INFO [sqlalchemy.engine.base.Engine:686][MainThread] COMMIT
2016-02-12 01:06:36,383 INFO [sqlalchemy.engine.base.Engine:646][MainThread] BEGIN (implicit)
2016-02-12 01:06:36,384 INFO [sqlalchemy.engine.base.Engine:1097][MainThread] INSERT INTO users (name, role, password_hash) VALUES (?, ?, ?)
2016-02-12 01:06:36,384 INFO [sqlalchemy.engine.base.Engine:1100][MainThread] ('editor', 'editor', '$2b$12$bSr5QR3wFs1LAnld7R94e.TXPj7DVoTxu2hA1kY6rm.Q3cAhD.AQO')
2016-02-12 01:06:36,384 INFO [sqlalchemy.engine.base.Engine:1097][MainThread] INSERT INTO users (name, role, password_hash) VALUES (?, ?, ?)
2016-02-12 01:06:36,384 INFO [sqlalchemy.engine.base.Engine:1100][MainThread] ('basic', 'basic', '$2b$12$.v0BQK2xWEQOnywbX2BFs.qzXo5Qf9oZohGWux/MOSj6Z.pVaY2Z6')
2016-02-12 01:06:36,385 INFO [sqlalchemy.engine.base.Engine:1097][MainThread] INSERT INTO pages (name, data, creator_id) VALUES (?, ?, ?)
2016-02-12 01:06:36,385 INFO [sqlalchemy.engine.base.Engine:1100][MainThread] ('FrontPage', 'This is the front page', 1)
2016-02-12 01:06:36,385 INFO [sqlalchemy.engine.base.Engine:686][MainThread] COMMIT
View the application in a browser
---------------------------------
We can't. At this point, our system is in a "non-runnable" state; we'll need
to change view-related files in the next chapter to be able to start the
application successfully. If you try to start the application (See
:ref:`wiki2-start-the-application`), you'll wind
up with a Python traceback on your console that ends with this exception:
.. code-block:: text
ImportError: cannot import name MyModel
This will also happen if you attempt to run the tests.
|
