Database Reference
In-Depth Information
Begin by firing up Python:
Python 2.6.6 (r266:84292, Oct 12 2012, 14:23:48)
[GCC 4.4.6 20120305 (Red Hat 4.4.6-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.>>>
The standard driver for Python is called PyMongo, and it was written by Mike Dirolf. Because the PyMongo driver
is supported directly by MongoDB, Inc., the company that publishes MongoDB, you can rest assured that it will be
regularly updated and maintained. So, let's go ahead and import the library. You should see something like the following:
>>> from pymongo import Connection
>>> import gridfs
>>>
If PyMongo isn't installed correctly, you will get an error similar to this:
>>> import gridfs
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named gridfs
>>>
If you see the latter message, chances are something was missed during installation. In that case, pop back to
Chapter 2 and follow the instructions to install PyMongo again.
Connecting to the Database
Before you can retrieve information from a database, you must first establish a connection to it. When you were using
the
mongofiles
utility earlier in this chapter, you probably noticed the reference to
127.0.0.1
. This value is also
known as the
localhost
, and it represents your computer's loopback address. This value is simply a shortcut for telling
a computer to talk to itself. The reason
mongofiles
mentioned this IP address is that it was actually connecting to
MongoDB through the network. The default is to connect to the local machine on the default MongoDB port. Because
you haven't changed the default settings,
mongofiles
can find and connect to your database without any trouble.
When using MongoDB with Python, however, you need to connect to the database and then set up GridFS.
Fortunately, this is easy to do:
>>> db = Connection().test
>>> fs = gridfs.GridFS(db)
>>>
The first line opens the connection and selects the database. By default,
mongofiles
uses the
test
database;
hence, you'll find your dictionary file in
test
. The second line sets up GridFS and prepares it for use.
Accessing the Words
In its original implementation, the PyMongo driver used a file-like interface to leverage GridFS. This is somewhat
different from what you saw in this chapter's earlier examples with
mongofiles
, which were more FTP-like in nature.
In the original implementation of PyMongo, you could read and write data just as you do for a normal file.
This made PyMongo very much like Python to use, and it allowed for easy integration with existing scripts.
However, this behavior was changed in version 1.6 of the driver, and this functionality is no longer supported. While
very Python-like, the behavior had some problems that made the tool less effective overall.
