Python, xml, databases, ...

[Zunbeltz Izaola]

Hi!

I am planning a program and I need some advice about what tool to use.

Basically my program will deal with a object A. A is a list like
object with same attributtes and a list of objects B. B is also a list
like object with attributes and a list of object C.

class A:
Name = ""
...
List = [] # List of B

class B:
Name = ""
...
List = [] # List of C

....

I want to store the information in a A object in a file. The structure
is a tree-like structure and I think XML is a good choice. I want to
know what model SAX or DOM, will be better to write/read the
information from the file. Is posible the files to get big (>1MB) and
the XML HOWTO recommend to use SAX, is that ok? what would be eaiser?

In a future i want to be able to do search and in different instances
of object A. I think i can storoe the information in a database
format. What tool are suitable for this task? I have read somethin
about MySQL and PostgreSQL, but i think they are only for servers, no
for program, is that all right?

I would build a GUI for the program (presumibly with wxPython). I want
to separate the GUI layer from the program layer. For comunication of
this two layer I have think in asyncore, but i have read something
about twisted and piro. Can anyone give my his/her opinion about this?

Thanks in advance

Zunbeltz

 

[Rasjid Wilcox]

I want to store the information in a A object in a file. The structure
is a tree-like structure and I think XML is a good choice. I want to
know what model SAX or DOM, will be better to write/read the
information from the file. Is posible the files to get big (>1MB) and
the XML HOWTO recommend to use SAX, is that ok? what would be eaiser?

In a future i want to be able to do search and in different instances
of object A. I think i can storoe the information in a database
format.

I think you want to be clear whether you want a database or not. If you
want to put the data into a database, you probably do not want to also put
it into a file structure. Although you certainly could then store to file
in the database, I think you would end up loosing the usefulness of one or
the other (or both).

What tool are suitable for this task? I have read somethin
about MySQL and PostgreSQL, but i think they are only for servers, no
for program, is that all right?

What do you mean by 'they are only for servers'?

Any machine can run a service (such as MySQL or PostgreSQL), and if it
offers that service to other machines then it is acting as 'server', or it
can just use it locally.

What platform are you planning to run this on? If it is Linux, then either
MySQL or PostgreSQL are easy options - most distros have pre-compiled
versions out of the box.

On Windows, both MySQL and PostgreSQL rely on the Cygwin dll. It looks like
MySQL has an easier Windows install, but their use of the cygwin dll
outside of Cygwin proper has serious stability consequences if the user
installs another cygwin based program. PostgreSQL is a 'proper' cygwin
program, but will be harder for non-unix/linux people to
install/administer.

You could also consider Firebird (http://firebird.sourceforge.net/) it has a
native Windows version as well as a Unix/Linux version) or SQLite
(http://www.hwaci.com/sw/sqlite/) with PySQLite
(http://pysqlite.sourceforge.net/manual.html).

There is also GadflyB5 (http://gadfly.sourceforge.net/) which looks like it
is written in pure python. There are probably other options too.

I would build a GUI for the program (presumibly with wxPython). I want
to separate the GUI layer from the program layer. For comunication of
this two layer I have think in asyncore, but i have read something
about twisted and piro. Can anyone give my his/her opinion about this?

Funny, I asked almost the same question about 20 minutes before you did.

Cheers,

Rasjid.

 

[Zunbeltz Izaola]

I think you want to be clear whether you want a database or not. If you

want to put the data into a database, you probably do not want to also put
it into a file structure. Although you certainly could then store to file
in the database, I think you would end up loosing the usefulness of one or
the other (or both).

I think i prefer first to store the information in a file. And then
see while the program is growing if it worth to use a database.

What do you mean by 'they are only for servers'?

Any machine can run a service (such as MySQL or PostgreSQL), and if it
offers that service to other machines then it is acting as 'server', or it
can just use it locally.

Up, I concept missundertand of mine. I want to know if
MySQL/PostgreSQL are only used in large web servers and such things,
or are also used in small programs that both the server and client
runs localy.

What platform are you planning to run this on? If it is Linux, then either
MySQL or PostgreSQL are easy options - most distros have pre-compiled
versions out of the box.

I want to have the program in both linux and windows.

On Windows, both MySQL and PostgreSQL rely on the Cygwin dll. It looks like
MySQL has an easier Windows install, but their use of the cygwin dll
outside of Cygwin proper has serious stability consequences if the user
installs another cygwin based program. PostgreSQL is a 'proper' cygwin
program, but will be harder for non-unix/linux people to
install/administer.

You could also consider Firebird (http://firebird.sourceforge.net/) it has a
native Windows version as well as a Unix/Linux version) or SQLite
(http://www.hwaci.com/sw/sqlite/) with PySQLite
(http://pysqlite.sourceforge.net/manual.html).

There is also GadflyB5 (http://gadfly.sourceforge.net/) which looks like it
is written in pure python. There are probably other options too.

Can you give me an advaice about what has a better easy to
use/performance ratio.

Funny, I asked almost the same question about 20 minutes before you did.

I have no see the question yet
Cheers,

zunbeltz

 

[Rasjid Wilcox]

Zunbeltz Izaola wrote:

Up, I concept missundertand of mine. I want to know if
MySQL/PostgreSQL are only used in large web servers and such things,
or are also used in small programs that both the server and client
runs localy.

I've definitely seen MySQL used where both server and client run locally,
and I'm sure there is plenty of the same with PostgreSQL.

I want to have the program in both linux and windows.


Can you give me an advaice about what has a better easy to
use/performance ratio.

Unfortunately, no, since I'm at about the same stage you are (ie, trying to
work out what to use).

I have _personally_ rulled out MySQL on Windows (due to it packaging the
cygwin dll in a non-standard way, since I use Cygwin at work), and will
only consider PostgreSQL on Windows if I can make the install trivial for a
non-technical user.

SQLite does not support Foreign Key constraints, so I think it is out for
me. Gadfly is not multi-user, so it is also out for me also.

Firebird is the only full featured open-source database that I know of that
has native binaries (non-cygwin) for Windows, and also runs on Linux and
Mac (although a native Windows port of PostgreSQL is in progress).

Another option that I have is to on Windows use the MDAC component and use a
MS Access backend database, and use MySQL or PostgreSQL on Linux/Mac.
See http://www.markcarter.me.uk/computing/python/ado.html for some info on
how to access a MS Access database from Python on Windows.

Without knowing what SQL feature set _you_ are after, it is impossible to
know what is the best option for you.

I have no see the question yet

My question was entitled 'Building a GUI agnostic database application'.

Cheers,

Rasjid.

 

[Zunbeltz Izaola]

Unfortunately, no, since I'm at about the same stage you are (ie, trying to
work out what to use).

I have _personally_ rulled out MySQL on Windows (due to it packaging the
cygwin dll in a non-standard way, since I use Cygwin at work), and will
only consider PostgreSQL on Windows if I can make the install trivial for a
non-technical user.

SQLite does not support Foreign Key constraints, so I think it is out for
me. Gadfly is not multi-user, so it is also out for me also.

Firebird is the only full featured open-source database that I know of that
has native binaries (non-cygwin) for Windows, and also runs on Linux and
Mac (although a native Windows port of PostgreSQL is in progress).

Another option that I have is to on Windows use the MDAC component and use a
MS Access backend database, and use MySQL or PostgreSQL on Linux/Mac.
See http://www.markcarter.me.uk/computing/python/ado.html for some info on
how to access a MS Access database from Python on Windows.

Without knowing what SQL feature set _you_ are after, it is impossible to
know what is the best option for you.

Thanks for your advaice and i will think more carefully what i nedd
and read information about the dbs you mention.

My question was entitled 'Building a GUI agnostic database application'.

I am reading it know.

thanks

Zunbeltz

 

[Joe Francia]

Hi!

I want to store the information in a A object in a file. The structure
is a tree-like structure and I think XML is a good choice. I want to
know what model SAX or DOM, will be better to write/read the
information from the file. Is posible the files to get big (>1MB) and
the XML HOWTO recommend to use SAX, is that ok? what would be eaiser?

Zunbeltz

In addition to the other suggestions made, you may want to consider the
embeddable Berkeley XML database, which may fit your needs better (or
not ;>):
http://www.sleepycat.com/download/index.shtml

If you are using Windows, you can get precompiled Python (and Java)
bindings here:
http://www.klamann-software.de/Community/index.html

Peace,
Joe