From 82511a6fe2d29d50c1cdca4b2abb23ff681a1943 Mon Sep 17 00:00:00 2001 From: Sebastian Silva Date: Wed, 16 Nov 2011 07:56:19 +0000 Subject: Major improvements in IDE usability. --- (limited to 'app/static/doc/flask-docs/tutorial/dbinit.html') diff --git a/app/static/doc/flask-docs/tutorial/dbinit.html b/app/static/doc/flask-docs/tutorial/dbinit.html new file mode 100644 index 0000000..413914e --- /dev/null +++ b/app/static/doc/flask-docs/tutorial/dbinit.html @@ -0,0 +1,166 @@ + + + + + + + + + Step 3: Creating The Database — Flask 0.8 documentation + + + + + + + + + + + + + + + + + + + + +
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Navigation

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Step 3: Creating The DatabaseΒΆ

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Flaskr is a database powered application as outlined earlier, and more +precisely, an application powered by a relational database system. Such +systems need a schema that tells them how to store that information. So +before starting the server for the first time it’s important to create +that schema.

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Such a schema can be created by piping the schema.sql file into the +sqlite3 command as follows:

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sqlite3 /tmp/flaskr.db < schema.sql
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The downside of this is that it requires the sqlite3 command to be +installed which is not necessarily the case on every system. Also one has +to provide the path to the database there which leaves some place for +errors. It’s a good idea to add a function that initializes the database +for you to the application.

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If you want to do that, you first have to import the +contextlib.closing() function from the contextlib package. If you +want to use Python 2.5 it’s also necessary to enable the with statement +first (__future__ imports must be the very first import):

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from __future__ import with_statement
+from contextlib import closing
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Next we can create a function called init_db that initializes the +database. For this we can use the connect_db function we defined +earlier. Just add that function below the connect_db function:

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def init_db():
+    with closing(connect_db()) as db:
+        with app.open_resource('schema.sql') as f:
+            db.cursor().executescript(f.read())
+        db.commit()
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The closing() helper function allows us to keep a +connection open for the duration of the with block. The +open_resource() method of the application object +supports that functionality out of the box, so it can be used in the +with block directly. This function opens a file from the resource +location (your flaskr folder) and allows you to read from it. We are +using this here to execute a script on the database connection.

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When we connect to a database we get a connection object (here called +db) that can give us a cursor. On that cursor there is a method to +execute a complete script. Finally we only have to commit the changes. +SQLite 3 and other transactional databases will not commit unless you +explicitly tell it to.

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Now it is possible to create a database by starting up a Python shell and +importing and calling that function:

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>>> from flaskr import init_db
+>>> init_db()
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Troubleshooting

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If you get an exception later that a table cannot be found check that +you did call the init_db function and that your table names are +correct (singular vs. plural for example).

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Continue with Step 4: Request Database Connections

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Related Topics

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This Page

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+ © Copyright 2010, Armin Ronacher. + Created using Sphinx. +
+ + \ No newline at end of file -- cgit v0.9.1