The Mouse Vs. The Python

If you have followed this blog for a while, you may remember that we’ve covered several XML parsing libraries that are included with Python. In this article, we’ll be continuing that series by taking a quick look at the ElementTree library. You will learn how to create an XML file, edit XML and parse the XML. For comparison’s sake, we’ll use the same XML we used in the previous minidom article to illustrate the differences between using minidom and ElementTree. Here is the original XML:

< ?xml version="1.0" ?>
<zappointments reminder="15">
    <appointment>
        <begin>1181251680</begin>        
        <uid>040000008200E000</uid>
        <alarmtime>1181572063</alarmtime>
        <state></state>
        <location></location>
        <duration>1800</duration>
        <subject>Bring pizza home</subject>
    </appointment>
</zappointments>

Now let’s dig into the Python! (more…)

When I was a kid, I was really into secret codes and ciphers. I thought they were all kinds of fun. My mom thought it would be fun to use some of the ciphers I was so enamored with in treasure hunts for special occasions, like birthdays. She would take something like a Cryptograph Wheel and create codes with it that my brother and I would have to decode with our own wheel to find a gift or another clue. We used stuff where numbers would represent letters (a=1, b=2, c=3) or we would use a sliding scale where you move the alphabet one letter over so A=B, C=D, D=E, etc. Sometimes we’d create a code stick where you get a long string of paper and wrap it around a pencil and then write a message of the paper. It’s pretty much impossible to read when it’s unwrapped.

Anyway, I decided to create a silly cipher program with wxPython where I could input a string and have it convert it to something else. I also wanted my program to decode it too. Now you can’t really make a program that can use a Cryptograph Wheel or a code stick, but for number codes or slide scales, that’s extremely easy. (more…)

The PySide GUI toolkit for Python has several standard dialogs and message boxes that you can use as-is. You can also create custom dialogs, but we’ll be saving that for a future article. In this post, we will cover the following dialogs:

• Color Dialog
• File Dialog
• Font Dialog
• Input Dialog
• Print & Print Preview Dialogs

We will also cover PySide’s Message Boxes. All code in this article was tested on Windows 7 Professional with PySide 1.2.2 and Python 2.6.6. Now let’s get to it! (more…)

As I learn PyQt and PySide, I am writing some tutorials to help my fellow travelers. Today we’ll be looking at how to connect multiple widgets to the same slot. In other words, we’ll be binding the widgets signals (basically events) to slots (i.e. callables like functions, methods) which are better known as “event handlers”. Yes, I know in PySide land that you don’t call it that. It’s a SLOT, not an event handler. But I digress. Anyway, there are two ways to approach this. One is to use functools and its partial class to pass parameters or to use PySide’s introspection abilities to grab that information from the widget that did the calling. There’s actually at least one other method that is very similar to functools.partial and that is to use the infamous anonymous function utility known as lambda. Let’s take a look at how all these methods can be done! (more…)

I am currently reading through Mark Summerfield’s book on PyQt, Rapid GUI Programming with Python and Qt and thought it would be fun to take some of the example applications in it and convert them to PySide. So I’ll be creating a series of articles where I’ll show the original PyQt examples from the book and then convert them to PySide and probably add something of my own to the code. The book doesn’t really get in Qt GUI coding until chapter 4 where the author creates a fun little currency converter. Come along and enjoy the fun! (more…)

The Reportlab library is a great way to generate PDFs in Python. Recently, I noticed that it has the ability to do barcodes. I had heard about it being able to generate QR codes, but I hadn’t really dug under the covers to see what else it could do. In this tutorial, we’ll take a look at some of the barcodes that Reportlab can generate. If you don’t already have Reportlab, go to their website and get it before jumping into the article. (more…)

This week, I needed to figure out how to attach an event handler that would fire when I double-clicked an item (i.e. row) in an ObjectListView widget that was in LC_REPORT mode. For some reason, there isn’t an obvious mouse event for that. There is an EVT_LIST_ITEM_RIGHT_CLICK and an EVT_LIST_ITEM_MIDDLE_CLICK, but nothing for LEFT clicks of any sort. After a bit of searching on Google, I found that I can get it to work by using EVT_LIST_ITEM_ACTIVATED. This will fire when an item is double-clicked and when an item is selected and the user presses ENTER. Here’s a code example:

import wx
from ObjectListView import ObjectListView, ColumnDefn
 
########################################################################
class Results(object):
    """"""
 
    #----------------------------------------------------------------------
    def __init__(self, tin, zip_code, plus4, name, address):
        """Constructor"""
        self.tin = tin
        self.zip_code = zip_code
        self.plus4 = plus4
        self.name = name
        self.address = address
 
 
########################################################################
class DCPanel(wx.Panel):
    """"""
 
    #----------------------------------------------------------------------
    def __init__(self, parent):
        """Constructor"""
        wx.Panel.__init__(self, parent=parent)
 
        mainSizer = wx.BoxSizer(wx.VERTICAL)
 
        self.test_data = [Results("123456789", "50158", "0065", "Patti Jones",
                                  "111 Centennial Drive"),
                          Results("978561236", "90056", "7890", "Brian Wilson",
                                  "555 Torque Maui"),
                          Results("456897852", "70014", "6545", "Mike Love", 
                                  "304 Cali Bvld")
                          ]
        self.resultsOlv = ObjectListView(self, style=wx.LC_REPORT|wx.SUNKEN_BORDER)
        self.resultsOlv.Bind(wx.EVT_LIST_ITEM_ACTIVATED, self.onDoubleClick)
 
        self.setResults()
 
        mainSizer.Add(self.resultsOlv, 1, wx.EXPAND|wx.ALL, 5)
        self.SetSizer(mainSizer)
 
    #----------------------------------------------------------------------
    def onDoubleClick(self, event):
        """
        When the item is double-clicked or "activated", do something
        """
        print "in onDoubleClick method"
 
    #----------------------------------------------------------------------
    def setResults(self):
        """"""
        self.resultsOlv.SetColumns([
            ColumnDefn("TIN", "left", 100, "tin"),
            ColumnDefn("Zip", "left", 75, "zip_code"),
            ColumnDefn("+4", "left", 50, "plus4"),
            ColumnDefn("Name", "left", 150, "name"),
            ColumnDefn("Address", "left", 200, "address")
            ])
        self.resultsOlv.CreateCheckStateColumn()
        self.resultsOlv.SetObjects(self.test_data)
 
 
########################################################################
class DCFrame(wx.Frame):
    """"""
 
    #----------------------------------------------------------------------
    def __init__(self):
        """Constructor"""
        wx.Frame.__init__(self, parent=None, title="Double-click Tutorial")
        panel = DCPanel(self)
 
#----------------------------------------------------------------------
if __name__ == "__main__":
    app = wx.App(False)
    frame = DCFrame()
    frame.Show()
    app.MainLoop()

Pretty straight-forward, right? I hope it’ll help you if you ever need to know how to do this. This method should work with a ListCtrl as well.

This week I spent some time learning how to add check boxes to the ObjectListView widget in wxPython. If you don’t know, ObjectListView is a 3rd party wrapper for the wx.ListCtrl widget that makes using the ListCtrl much easier. You can read all about it in this older article from the archives. I had a requirement where I needed to have a check box next to each item in the report view of the widget. After some digging on the ObjectListView website, I found an article that sort of explained how to do it. According to the documentation, I could use the CreateCheckStateColumn method or register a column and use InstallCheckStateColumn. In this article, we’ll be focusing on the CreateCheckStateColumn method. (more…)

Last week I was contacted about a cool sounding book project on Kickstarter: Real Python for Web Development, featuring web2py by Michael Herman. I have to admit that I’m not familiar with Mr. Herman or the person who originally contacted me about the book, but since I enjoy reading Python books and this one sounded interesting, I thought I’d let my readers know about it too. You can support the project yourself if you want. He’s recently added some tutorials for Flask to the book, so you can learn a little about two Python web frameworks!

The other day, I was trying to figure out if there was an easy way to grab a class’s defined attributes (AKA “instance variables”). The reason was that we were using the attributes we created to match up with the fields in a file we parse. So basically we read a file line-by-line and each line can be split into 150+ pieces that need to be mapped to the fields we create in the class. The catch is that we recently added more fields to the class and there’s a check in the code that is hard-coded with the number of fields that should be in the file. Thus, when I added more fields, it broke the check. I hope that all made sense. Now you know the background, so we can move on. I found three different ways to accomplish this, so we’ll go from the most complex to the simplest. (more…)