The wxPython toolkit added context managers to its code base a few years ago, but for some reason you don’t see very many examples of their use. In this article, we’ll look at three examples of context managers in wxPython. A wxPython user was the first person to suggest using context managers in wxPython on the wxPython mailing list. We’ll start off by rolling our own context manager and then look at a couple of examples of built-in context managers in wxPython.
The other day, I came across an interesting StackOverflow question where the fellow was trying to figure out how to open a sub-frame only once. Basically he wanted a single instance of the sub-frame (and other sub-frames). After digging around a bit on Google, I found an old thread from the wxPython Google Group that had an interesting approach to doing what was needed.
Basically it required a bit of meta-programming, but it was a fun little exercise that I thought my readers would find interesting. Here’s the code:
I recently came across a StackOverflow question where the fellow was asking how to get wxPython’s RichTextCtrl’s XML data so he could save it to a database. I don’t know much about this control, but after a quick Google search, I found an article from 2008 that gave me the information I needed. I took that example and cut it down to the following example:
I recently came across a fun little project called EasyGUI_Qt. It’s basically the same thing as EasyGUI except that it uses PyQt4 instead of Tkinter. The idea behind both of these packages is to allow the developer to ask the user simple questions using dialogs.
In this article, we’ll spend some time learning how to use this package by looking at a few examples. Note that EasyGUI_Qt works with both Python 2 and 3, although its primary target is Python 3. The documentation states that there may be some issues with unicode in Python 2, but other than that, the widgets should work fine.
The wxPython library comes with a pair of handy methods called Freeze() and Thaw(). The call to Freeze() prevents the window from updating while it is frozen. This can be useful when you are adding or removing widgets and you want to reduce your UI from appearing to flicker. After you finish updating the UI, then you call the Thaw() method so that the user will be able to see the update.
Let’s take a look at a simple example.
The wxPython GUI toolkit includes its own date / time capabilities. Most of the time, you can just use Python’s datetime and time modules and you’ll be fine. But occasionally you’ll find yourself needing to convert from wxPython’s wx.DateTime objects to Python’s datetime objects. You may encounter this when you use the wx.DatePickerCtrl widget.
Fortunately, wxPython’s calendar module has some helper functions that can help you convert datetime objects back and forth between wxPython and Python. Let’s take a look:
def _pydate2wxdate(date): import datetime assert isinstance(date, (datetime.datetime, datetime.date)) tt = date.timetuple() dmy = (tt, tt-1, tt) return wx.DateTimeFromDMY(*dmy) def _wxdate2pydate(date): import datetime assert isinstance(date, wx.DateTime) if date.IsValid(): ymd = map(int, date.FormatISODate().split('-')) return datetime.date(*ymd) else: return None
You can use these handy functions in your own code to help with your conversions. I would probably put these into a controller or utilities script. I would also rewrite it slightly so I wouldn’t import Python’s datetime module inside the functions. Here’s an example:
import datetime import wx def pydate2wxdate(date): assert isinstance(date, (datetime.datetime, datetime.date)) tt = date.timetuple() dmy = (tt, tt-1, tt) return wx.DateTimeFromDMY(*dmy) def wxdate2pydate(date): assert isinstance(date, wx.DateTime) if date.IsValid(): ymd = map(int, date.FormatISODate().split('-')) return datetime.date(*ymd) else: return None
You can read more about this topic on this old wxPython mailing thread. Have fun and happy coding!
Redirecting stdout seems to be a pretty common request on the wxPython users group, so I decided to see how easy it would be to do it with Tkinter. The typical use case for redirecting stdout or stderr is that you are calling some other process (like ping or tracert) and you want to catch what it’s doing to put it into your UI. Usually you can just use Python’s subprocess module and call its communicate() method to access the data. Then you can just print it to stdout and it will magically appear in your UI’s widget of choice.
Our finished user interface will look something like the following:
Let’s find out how to do this with Tkinter: Continue reading Tkinter – Redirecting stdout / stderr
I’ve been using wxPython for quite a while now and I see certain questions come up on a fairly frequent basis. One of the popular ones is how to ask the user for their credentials before loading up the rest of the application. There are several approaches to this, but I am going to focus on a simple solution as I believe this solution can be used as the basis for more complex solutions.
Basically what we want to happen is for the user to see a login dialog where they have to enter their username and password. If they enter it correctly, then the program will continue to load and they’ll see the main interface. You see this a lot on websites with a common use case being web email clients. Desktop applications don’t include this functionality as often, although you will see it for Stamps.com’s application and for law enforcement software. We will be creating a dialog that looks like this:
Kivy is a neat package that allows Python developers to create user interfaces on mobile devices. You can also deploy the applications to desktops too. This is the second book I’ve seen put out on the subject. The first book, Kivy – Interactive Applications in Python by Roberto Ulloa came out last year from Packt Publishing. This year, we have Dusty Phillips’ work, Creating Apps in Kivy from O’Reilly. I will be reviewing the PDF version of the book.
- Why I picked it up:I picked this book up because I like the author’s previous work, Python 3 Object Oriented Programming
- Why I finished it: The book is pretty short and it’s interesting
- I’d give it to: Someone who already knows Python
Kivy is an open source Python library for rapid development of applications that make use of innovative user interfaces, such as multi-touch apps. The Kivy organization is organizing its second application development contest.! This is a great chance for new and experienced users to show off their skills and compete for prizes. Entries will be judged on a range of criteria accessible to both new and experienced programmers, so don’t be afraid to dive in! For more information, visit http://kivy.org/#contest