from __future__ import print_function from __future__ import unicode_literals from builtins import str, bytes, dict, int import os import sys sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "..")) from pattern.server import App, Database, html # This example demonstrates a web app with a simple database back-end. # The pattern.server module has a Database object # that can be used with SQLite and MySQL databases. # SQLite is part of Python 2.5+. # MySQL requires the mysql-python bindings (http://sourceforge.net/projects/mysql-python/). app = App("store") # In this example we'll use SQLite. # The advantage is that you don't need to install anything, # and that the database is a file at a location of your choice. # We use SQLite Database browser (Mac OS X) to browse the file. # (http://sourceforge.net/projects/sqlitebrowser/) # The disadvantage is that SQLite is not multi-threaded. # This will lead to problems ("database is locked") in larger projects. # The app server uses multiple threads to handle concurrent requests. # If two request want to write to the database at the same time, # one of them will have to wait while the other finishes writing. # If enough requests are waiting in line, the database may crash. # The next example uses a DatabaseTransaction to remedy this. # Reading from the database is no problem. # The following code creates a new database "store.db", # in the same folder as this script. # Databases can be queried and modified with SQL statements. # The SQL code below creates a "products" table in the database. # Each table has fields (or columns) with a type (text, int, float, ...). STORE = os.path.join(os.path.dirname(__file__), "store.db") if not os.path.exists(STORE): db = Database(STORE, schema=""" create table if not exists `products` ( `id` integer primary key autoincrement, `name` text, `price` float ); create index if not exists products_name on products(name); """ ) # Add some rows of data to the "products" table: db.execute("insert into `products` (name, price) values (?, ?)", values=("rubber chicken", "199"), commit=False) db.execute("insert into `products` (name, price) values (?, ?)", values=("donkey costume", "249"), commit=False) db.execute("insert into `products` (name, price) values (?, ?)", values=("mysterious box", "999"), commit=False) db.commit() # The most interesting part in this example is the code below. # Because the server is multi-threaded, # each separate thread needs its own Database object. # This is handled for us by using @app.bind(). # It creates an optional parameter "db" that is available in every URL handler, # and which contains a connection to the database for the active thread. @app.bind("db") def db(): return Database(STORE) # Note how the path handler for http://127.0.0.1:8080/products # takes the optional parameter "db". # For http://127.0.0.1:8080/products, it displays an overview of all products. # For http://127.0.0.1:8080/products/rubber-chicken, it displays the product with the given name. # The html.table() helper function returns a HTML-string with a