[Tutor] database applications with Python - where to start
Hi, this is one of those difficult questions about where to start! I want to create a book-keeping/accounting application for my own use 1. because I can't find any that suits me, and 2. because I want to improve and extend my knowledge of Python. Clearly this is going to be a database application - the trouble is, that despite reading loads of stuff (including previous posts here on the topic), I get a Catch-22 feeling that I need to be an expert with 'the big picture' before I can even take my first stumbling steps towards becoming that expert! Also the trouble with reading stuff on the web is that you don't know who is an out-on-a-limb lunatic, and who is talking sense backed up with concrete experience. And of course, quite understandably, everyone wants you to use *their* module/driver/database/whatever. Here's where I am: I have a reasonable grasp of Python (but realise that I have a lot still to learn). I have written database applications before, but only using MS Access (both with its own Jet database and with MSDE/SQL-Server) - no major boasts here, let's just say they *worked*! The thing is, Access rather pampers you with visual tools for doing many aspects of the work, and even a neat little environment to manage your code. Now I want to move on, and use Python, probably with a RDBMS. I haven't chosen the database - difficult again, because although this will be a small application, it is accounting data, so its integrity is paramount, and certain inviolable constraints must be built in at a very fundamental level (the data needs protection from my code!!). I will also obviously need a UI, probably a GUI (but it would be nice to keep my options open to do a web UI version at some point). So here's the thing. Even though I have quite a clear idea of what the database schema will look like, and what the UI will *do* (even though I don't know what it will look like), I'm having real trouble understanding how/where to start. I'm tempted to try to put together a 'kit' of tools (as visual as possible) to emulate what I'm used to - but is this a good idea? and if so, which tools? What on earth is my application's model going to look like? should I get involved with object-relational mapping? how much work should I delegate to the RDBMS, and how much logic should I code in Python? Should I even be thinking radically and ditch the RDBMS in favour of something like a 'Prevalence Layer' that I have read about? what should inform these decisions? I just don't know where to start! A book perhaps, but then, which one? Or maybe an example app for me to pick apart and learn from? Sorry it is such a vague question, but any pointers gratefully received. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] database applications with Python - where to start
On Thu, May 05, 2005 at 02:03:30PM +0100, Barnaby Scott wrote: Hi, this is one of those difficult questions about where to start! I want to create a book-keeping/accounting application for my own use 1. because I can't find any that suits me, and 2. because I want to improve and extend my knowledge of Python. Good reasons for doing something - just remember that, as you are discovering, this is a pretty extensive project, and the reasons need to be good enough if you are to finish. Clearly this is going to be a database application - the trouble is, that despite reading loads of stuff (including previous posts here on the topic), I get a Catch-22 feeling that I need to be an expert with 'the big picture' before I can even take my first stumbling steps towards becoming that expert! This is a very reasonable response when you look at a project and begin to appreciate its complexities. I am the opposite of a Python expert (most of the code I read leaves me with questions and confusion - that's why I'm lurking here), but I know something about problem-solving. Here is an approach that may help: Programming is, by definition, something that can be decomposed into smaller problems. When you are thinking about your project, write everything you think of down. Once it is written down, attempt to break up your notes into categories - features, behaviours, functional activities of the finished product. This does not need to take a long time. Once you think you have a collection of things you need from your project (these are called Requirements by many), try to organize them by type: data storage, data manipulation, human interfaces, computer systems interfaces, etc. Now, take one of these aspects at a time, and try to quantify what exactly this piece of the project needs to do - for example, write data into a database. Once you have in your head a clear picture of one activity of your program, write a small piece of code that does what you want. If it doesn't work, ask for help - small problems are easier to solve (generally) than big ones, and always easier to ask for help about. Something that helps is to make each proof of concept script with a name that relates back to your Requirements document - so you know by the file name how it fits in the whole project. At some point you will have to commit to which tools you are going to use (database, language, interface, etc.). For your first major project, try to use what you know, or what you have the best support systems in place for - local gurus, lists, user groups etc. Even while you commit to one set of tools, try to think of your program as a set of interacting pieces that can be abstracted from one another, so if you need to change one piece the whole structure doesn't collapse (this is called loose coupling). how/where to start. I'm tempted to try to put together a 'kit' of tools (as visual as possible) to emulate what I'm used to - but is this a good idea? and if so, which tools? Tool kits are very worthwhile - once you have code that works, you'll reuse it a lot. Which tools comes down to an optimization of your ability and comfort, your support network and features. What on earth is my application's model going to look like? should I get involved with object-relational mapping? If it will gain you something yes, if you don't understand what the gains are or how to implement them, probably not. how much work should I delegate to the RDBMS, and how much logic should I code in Python? If you decide at some other point to change databases, delegating core functions to the database may hurt. If you decide to re-write your project in C later, you may regret not handing some things to the database. In all cases, try not to reinvent the wheel habitually, but only where it serves a purpose (learning how it works is a purpose). Should I even be thinking radically and ditch the RDBMS in favour of something like a 'Prevalence Layer' that I have read about? what should inform these decisions? What do you *really* understand, and what can you implement without having an aneurysm. I just don't know where to start! A book perhaps, but then, which one? Or maybe an example app for me to pick apart and learn from? Look for an Open Source app that almost works the way you need it to, and look at how it's done. You may find that getting involved with an existing project will get you the features you need sooner than building something from scratch, and by getting involved you can learn a lot. Sorry it is such a vague question, but any pointers gratefully received. Vague questions are hard to answer specifically, but they are often worth asking. You may find more success decomposing your vague questions into specific sub-questions - they are easier to answer quickly. -- yours, William signature.asc Description: Digital signature ___ Tutor maillist - Tutor@python.org
Re: [Tutor] database applications with Python - where to start
Well I'm currently working on a database programmers guide for my tutorial and I'm happy to send you what I've done so far - but its only half complete. However any feedback would be good. (It assumes the use of SQLite as the actual database) Alan G. PS It'll probably be another month at least before its fully done! I've got an awful lot in my diary just now! - Original Message - From: Barnaby Scott [EMAIL PROTECTED] To: tutor@python.org Sent: Thursday, May 05, 2005 2:03 PM Subject: [Tutor] database applications with Python - where to start Hi, this is one of those difficult questions about where to start! I want to create a book-keeping/accounting application for my own use 1. because I can't find any that suits me, and 2. because I want to improve and extend my knowledge of Python. Clearly this is going to be a database application - the trouble is, that despite reading loads of stuff (including previous posts here on the topic), I get a Catch-22 feeling that I need to be an expert with 'the big picture' before I can even take my first stumbling steps towards becoming that expert! Also the trouble with reading stuff on the web is that you don't know who is an out-on-a-limb lunatic, and who is talking sense backed up with concrete experience. And of course, quite understandably, everyone wants you to use *their* module/driver/database/whatever. Here's where I am: I have a reasonable grasp of Python (but realise that I have a lot still to learn). I have written database applications before, but only using MS Access (both with its own Jet database and with MSDE/SQL-Server) - no major boasts here, let's just say they *worked*! The thing is, Access rather pampers you with visual tools for doing many aspects of the work, and even a neat little environment to manage your code. Now I want to move on, and use Python, probably with a RDBMS. I haven't chosen the database - difficult again, because although this will be a small application, it is accounting data, so its integrity is paramount, and certain inviolable constraints must be built in at a very fundamental level (the data needs protection from my code!!). I will also obviously need a UI, probably a GUI (but it would be nice to keep my options open to do a web UI version at some point). So here's the thing. Even though I have quite a clear idea of what the database schema will look like, and what the UI will *do* (even though I don't know what it will look like), I'm having real trouble understanding how/where to start. I'm tempted to try to put together a 'kit' of tools (as visual as possible) to emulate what I'm used to - but is this a good idea? and if so, which tools? What on earth is my application's model going to look like? should I get involved with object-relational mapping? how much work should I delegate to the RDBMS, and how much logic should I code in Python? Should I even be thinking radically and ditch the RDBMS in favour of something like a 'Prevalence Layer' that I have read about? what should inform these decisions? I just don't know where to start! A book perhaps, but then, which one? Or maybe an example app for me to pick apart and learn from? Sorry it is such a vague question, but any pointers gratefully received. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
