I'm currently attempting to migrate a legacy VBA/Microsoft Access application to Python and PyQt. I've had no problems migrating any of the logic, and most of the forms have been a snap, as well. However, I've hit a problem on the most important part of the application--the main data-entry form.
The form is basically a row of text boxes corresponding to fields in the database. The user simply enters data in to a fields, tabs to the next and repeats. When he comes to the end of the record/row, he tabs again, and the form automatically creates a new blank row for him to start entering data in again. (In actuality, it displays a "blank" row below the current new record, which the user can actually click in to to start a new records as well.) It also allows the user to scroll up and down to see all the current subset of records he's working on.
Is there a way to replicate this functionality in PyQt? I haven't managed to find a way to get Qt to do this easily. Access takes care of it automatically; no code outside the form is required. Is it that easy in PyQt (or even close), or is this something that's going to need to be programmed from scratch?
You should look into QSqlTableModel, and the QTableView Objects. QSqlTableModel offers an abstraction of a relational table that can be used inside on of the Qt view classes. A QTableView for example. The functionality you describe can be implemented with moderate effort just by using these two classes.
The QSqlTableModel also supports editing on database fields.
My guess the only functionality that you will have to manually implement is the "TAB" at the end of the table to create a new row if you want to keep that.
I don't know much about Access, but using the ODBC-SQL driver you should be able use the actual access database for your development or testing there is some older information here, you might want to consider moving to Sqlite, Mysql or another actual SQL database.
Related
I've got a .mdb that opens with the ability to select a value from a drop down (Setup Main window with Pragram Data field). This then generates the Setup Data window. This information is all pulled from relationships between different tables, yet when I view relationships there are no connections between the tables? The small buttons to the mid/upper right (Op sheet, Tool Sheet, etc) all generate a report to be printed. I also cannot find where these reports come from or the connections between them and the Setup Data window. Anyone familiar with MS Access can give some guidance into viewing these things?
My goal is to recreate these reports in a Python Pandas dataframe or similar. I've connected to the .mdb using pyodbc already and can load them into a df but am unsure how these connections are made?
You can try holding the [Shift] key down as you open the database in Access. That may bypass the startup code (if the developer hasn't disabled that feature) and allow you to open the Form(s) in Design View. From there you can inspect the Events associated with the Form controls to see what they do (e.g., a button Click event may call DoCmd.OpenReport to open a Report).
Specifically with regard to Relationships, the developer may have simply not bothered to define them in the Relationships window. However, you can still identify the relationships between the tables by looking at the JOINs in saved queries, including the queries defined as the Record Source of a Report.
I'm currently using a program called NiceLabel to create a form that prints labels for a production environment. The current idea is that there are 4 entry forms tied to a database, the first form will query and select the relevant entry in the database and the last entry fields would be for comparing the entries under their respective columns. If all the data in all the forms match it will allow you to print a label.
I have no practical experience actually developing, this is my first venture and I'm pretty lost. I have included a screenshot of the front end form itself, the program supports python/vb scripting and SQL queries.
I am working on a project which requires me to create a table of every user who registers on the website using the username of that user. The columns in the table are same for every user.
While researching I found this Django dynamic model fields. I am not sure how to use django-mutant to accomplish this. Also, is there any way I could do this without using any external apps?
PS : The backend that I am using is Mysql
An interesting question, which might be of wider interest.
Creating one table per user is a maintenance nightmare. You should instead define a single table to hold all users' data, and then use the database's capabilities to retrieve only those rows pertaining to the user of interest (after checking permissions if necessary, since it is not a good idea to give any user unrestricted access to another user's data without specific permissions having been set).
Adopting your proposed solution requires that you construct SQL statements containing the relevant user's table name. Successive queries to the database will mostly be different, and this will slow the work down because every SQL statement has to be “prepared” (the syntax has to be checked, the names of table and columns has to be verified, the requesting user's permission to access the named resources has to be authorized, and so on).
By using a single table (model) the same queries can be used repeatedly, with parameters used to vary specific data values (in this case the name of the user whose data is being sought). Your database work will move along faster, you will only need a single model to describe all users' data, and database management will not be a nightmare.
A further advantage is that Django (which you appear to be using) has an extensive user-based permission model, and can easily be used to authenticate user login (once you know how). These advantages are so compelling I hope you will recant from your heresy and decide you can get away with a single table (and, if you planning to use standard Django logins, a relationship with the User model that comes as a central part of any Django project).
Please feel free to ask more questions as you proceed. It seems you are new to database work, and so I have tried to present an appropriate level of detail. There are many pitfalls such as this if you cannot access knowledgable advice. People on SO will help you.
This page shows how to create a model and install table to database on the fly. So, you could use type('table_with_username', (models.Model,), attrs) to create a model and use django.core.management to install it to the database.
I am relatively new to database GUI programming, and I want to make a simple app in Python, which allows user to access and edit database. I want to view/edit tables and specific records plus generate some specific reports about stored data. For example, if we have a table with employees name and position, it should allow to edit name and select position from list and immediately change database according to changes. For one employee record it should output name and, again give a selectable list of positions. Also, it should have a dialog to add employees.
So, is there a way to create widgets for data tables and specific records which allows to output and edit data with automatic changes in database? I want to reduce the need for writing methods, which look at changes in view and reflect them at model.
I am using PyQt for writing GUI. Solutions for SQL, or ORMs like SQLAlchemy would both be fine.
You can use the Qt Database GUI Layer.
If you want to use SQLAlchemy too, you can take a look at Camelot.
UPDATE
A good introduction to the Qt Database GUI Layer is chapter 15 of the book
"Rapid GUI Programming with Python and Qt".
I'm a firm believer of the heretic thought of tight coupling between the backend and frontend: I want existing, implied knowledge about a backend to be automatically made use of when generating user interfaces. E.g., if a VARCHAR column has a maximum with of 20 characters, there GUIs should automatically constrain the user from typing more than 20 characters in a related form field.
And I have strong antipathy to ORMs which want to define my database tables, or are based on some hack where every table needs to have extra numeric ID columns because of the ORM.
I've looked a bit into Python database frameworks and I think I can conclude the SQLAlchemy fits best to my mentality.
Now, I need to find a web application framework which fits naturally with SQLAlchemy (or an equivalent) and perhaps even with my appetite for coupling. With "web application framework", I mean products/project such as Pyhons, Django, TurboGears, web2py, etc.
E.g., it should ideally be able to:
automatically select a suitable form widget for data entering a given column if told to do so; e.g., if the column has a foreign key to a column with 10 different values, widget should display the 10 possible values as a dropdown
auto-generate javascript form validation code which gives the end-user quick error feedback if a string is entered into a field which is about to end up in an INTEGER column, etc
auto-generate a calendar widget for data which will end up in a DATE column
hint NOT NULL constraints as javascript which complains about empty or whitespace-only data in a related input field
generate javascript validation code which matches relevant (simple) CHECK-constraints
make it easy to avoid SQL injection, by using prepared statements and/or validation of externally derived data
make it easy to avoid cross site scripting by automatically escape outgoing strings when appropriate
make use of constraint names to generate somewhat user friendly error messages in case a constrataint is violated
All this should happen dynamically, so table adjustments are automatically reflected on the frontend - probably with a caching mechanism, so that all the model introspection wouldn't kill performance. In other words, I don't want to repeat my model definition in an XML file (or alike) when it has already been carefully been defined in my database.
Does such a framework exist for Python (or for any language, for that matter)? If not: Which of the several Python web application frameworks will be least in the way if I were to add parts of the above features myself?
web2py does most of what you ask:
Based on a field type and its validators it will render the field with the appropriate widget. You can override with
db.table.field.widget=...
and use a third party widget.
web2py has js to blocks the user from entering a non-integer in a integer field or a non-double in a double field. time, date and datetime fields have their own pickers. These js validation work with (not instead) of server side validation.
There is IS_EMPTY_OR(...) validator.
The DAL prevents SQL injections since everthing is escaped when goes in the DB.
web2py prevents XSS because in {{=variable}}, 'variable' is escaped unless specified otherwise {{=XML(variable)}} or {{=XML(variable,sanitize=True)}}
Error messages are arguments of validators for example
db.table.field.requires=IS_NOT_EMPTY(error_message=T('hey! write something in here'))
T is for internationalization.
You should have a look at django and especially its newforms and admin modules. The newforms module provides a nice possibility to do server side validation with automated generation of error messages/pages for the user. Adding ajax validation is also possible
TurboGears currently uses SQLObject by default but you can use it with SQLAlchemy. They are saying that the next major release of TurboGears (1.1) will use SQLAlchemy by default.
I know that you specificity ask for a framework but I thought I would let you know about what I get up to here. I have just undergone converting my company's web application from a custom in-house ORM layer into sqlAlchemy so I am far from an expert but something that occurred to me was that sqlAlchemy has types for all of the attributes it maps from the database so why not use that to help output the right html onto the page. So we use sqlAlchemy for the back end and Cheetah templates for the front end but everything in between is basically our own still.
We have never managed to find a framework that does exactly what we want without compromise and prefer to get all the bits that work right for us and write the glue our selves.
Step 1. For each data type sqlAlchemy.types.INTEGER etc. Add an extra function toHtml (or many maybe toHTMLReadOnly, toHTMLAdminEdit whatever) and just have that return the template for the html, now you don't even have to care what data type your displaying if you just want to spit out a whole table you can just do (as a cheetah template or what ever your templating engine is).
Step 2
<table>
<tr>
#for $field in $dbObject.c:
<th>$field.name</th>
#end for
</tr>
<tr>
#for $field in dbObject.c:
<td>$field.type.toHtml($field.name, $field.value)</td>
#end for
</tr>
</table>
Using this basic method and stretching pythons introspection to its potential, in an afternoon I managed to make create read update and delete code for our whole admin section of out database, not yet with the polish of django but more then good enough for my needs.
Step 3 Discovered the need for a third step just on Friday, wanted to upload files which as you know needs more then just the varchar data types default text box. No sweat, I just overrode the rows class in my table definition from VARCHAR to FilePath(VARCHAR) where the only difference was FilePath had a different toHtml method. Worked flawlessly.
All that said, if there is a shrink wrapped one out there that does just what you want, use that.
Disclaimer: This code was written from memory after midnight and probably wont produce a functioning web page.
I believe that Django models does not support composite primary keys (see documentation). But perhaps you can use SQLAlchemy in Django? A google search indicates that you can. I have not used Django, so I don't know.
I suggest you take a look at:
ToscaWidgets
DBSprockets, including DBMechanic
Catwalk. Catwalk is an application for TurboGears 1.0 that uses SQLObject, not SQLAlchemy. Also check out this blog post and screencast.
FastData. Also uses SQLObject.
formalchemy
Rum
I do not have any deep knowledge of any of the projects above. I am just in the process of trying to add something similar to one of my own applications as what the original question mentions. The above list is simply a list of interesting projects that I have stumbled across.
As to web application frameworks for Python, I recommend TurboGears 2. Not that I have any experience with any of the other frameworks, I just like TurboGears...
If the original question's author finds a solution that works well, please update or answer this thread.