Graphics Contexts and DCs explanations?
Experimenting with graphics in an app: it's AUI based with a few panes, one of which has a panel containing a few sizers holding UI elements. One sizer contains a panel that needs some basic line-drawing graphics in it. I use the wxPython demo app heavily to figure this stuff out, and my experiments seem to work, but I'm flying blind somewhat. Can someone englighten me about the wx.GraphicsContext versus wx.PaintDC (BTW what does PaintDC stand for? Drawing Context perhaps?) The scrolledWindow and GraphicsContext examples are helpful, but it appears I can draw a rectangles, lines and text in either just a straight wxPaintDC, or can do: dc = wx.PaintDC(self) gc = wx.GraphicsContext.Create(dc) ...and do the same drawing with gc.DrawText etc... Can someone clarify the differences or added value of the gc over the dc, and is using the dc alone a valid approach? Where will it end up biting me - I don't mean which body part :) Perhaps I should say in which situation will it bite... Thx, Ross. -- http://mail.python.org/mailman/listinfo/python-list
Re: Graphics Contexts and DCs explanations?
Chris Mellon wrote: This is probably better suited to the wxPython ML instead of c.l.p, because it's so specific. In short: wxDC (and friends) are traditional raster based drawing contexts. wxGraphicsContext is a vector/path based API. If you're doing drawing that's suited for a vector format (like line drawing probably is), using wxGraphicsContext will give you better image quality as well as the general vector features like free scaling, rotation, transforms, etc, Thx Chris - I wasn't aware of the wxPython ML. I'll hunt around for it for further q's in that vein. Your explanation is helpful tho' - thx. -- http://mail.python.org/mailman/listinfo/python-list
Unexpected global variable behaviour
I'm seeing something which make me think I'm missing something about how global var's behave. I've defined a global string, right at the start of my .py file. outXMLfile = "abc" I define a class and do a bunch of stuff below that. Then I have another class, and in it, there is a method 'def' that has: def OnOutfileButton(self,evt): (fPath, fName)=os.path.split(fullName) print "Selected output file: " + fName outXMLfile = fName print "output file: " + outXMLfile Print statements in random other places in the project, show outXMLfile prints as "abc" however, in this def, it comes out as the same as fName (e.g. "myfile.xml") If the print line for outXMLfile is before the assignment to fName, it throws the error: UnboundLocalError: local variable 'outXMLfile' referenced before assignment If I remove the line that says "outXMLfile = fName" then the print statement gives me the value "abc" What am I missing? When I assign a value to update my global variable, it becomes a local variable. If I don't try to update it, it stays global. I assume it's acting like a constant, though I have a couple of global lists and I seem to be able to append to them okay. I guess I can move the variable into the parent class and get at it that way, but want to understand the error of my ways... Ross. -- http://mail.python.org/mailman/listinfo/python-list
Re: Unexpected global variable behaviour
Thanks a lot Fredrik, A big wave of deja vu came over me as I read your note. That bit me once before, and was my only previous run-in with the 'global' directive which clearly didn't stick with me. :( Thanks for the concise, helpful reply. The universe makes sense again. -Ross. Fredrik Lundh wrote: http://docs.python.org/ref/naming.html "If a name binding operation occurs anywhere within a code block, all uses of the name within the block are treated as references to the current block. This can lead to errors when a name is used within a block before it is bound." to fix this, use the global directive: http://docs.python.org/ref/global.html def OnOutfileButton(self,evt): global outXMLfile # flag variable as global fPath, fName = os.path.split(fullName) print "Selected output file:", fName outXMLfile = fName ... -- http://mail.python.org/mailman/listinfo/python-list
Global var access in imported modules?
I have a main module doStuff.py and another module utility.py. At the start of doStuff.py I call import utility.py Then I also proceed to initiallize some global variables sName = "" Then I create a class, some methods etc. In one of the methods I assign a value to my variable sName. Then I call a function from within my utility.py file: utility.makeOne(stuff) Within my utility.py file, I define the makeOne function. But I want to use that same global variable "sName" In utility.py I have tried to indicate that I'm using the global "sName" through the statement: global sName But when I go to use the variable it still gives me an error: NameError: global name 'sName' is not defined I thought perhaps I need to indicate 'globality' in my main module, so before I initiallized sName in doStuff.py I added: global sName But it doesn't help me. I had this issue before and resolved it by declaring the variable global in the sub-module utility.py, but then I needed to reference it in my main module with a prefix: utility.sName = "" It's more verbose,and defining globals in a submodule seems backward. But also, what if I need to access "sName" in another imported module, say "otherstuff.py"? I would do my "import otherstuff" call in my main module, but would I have to put an "import utility" into the otherstuff.py file? Is there some way I can define globals in my main module, and have them accessible in all my imported submodule? As you can see I'm a little unsure about the global handling in a multi-module environment. Any suggestions appreciated. I've read http://docs.python.org/ref/naming.html but it hasn't enlightened me on this one. -- http://mail.python.org/mailman/listinfo/python-list
Re: Global var access in imported modules?
Fredrik Lundh wrote: >>import utility.py > that tries to import a module named "py" from the package "utility". oops - that was just a typo in my post - I meant of course "import utility" > > Python doesn't have "program-wide global" variables; if you need that, > create a support module and import that module everywhere you need to > access those variables: > > # file: globalvars.py > sName = "" > > # file: myprogram.py > import globalvars > print globalvars.sName > > etc. > > > That's news - thanks, I didn't realize that there just wasn't the concept of program-wide globals. The support module idea sounds like a path forward. -R. -- http://mail.python.org/mailman/listinfo/python-list
Re: Global var access in imported modules?
Dennis Lee Bieber wrote: On Wed, 27 Aug 2008 16:21:03 -0400, RgeeK <[EMAIL PROTECTED]> declaimed the following in comp.lang.python: I have a main module doStuff.py and another module utility.py. At the start of doStuff.py I call import utility.py I hope not... import utility no .py Then I also proceed to initiallize some global variables Python does not have global variables. Names belong within a module (or within functions defined within the module). sName = "" Then I create a class, some methods etc. In one of the methods I assign a value to my variable sName. Then I call a function from within my utility.py file: utility.makeOne(stuff) Within my utility.py file, I define the makeOne function. But I want to use that same global variable "sName" In utility.py I have tried to indicate that I'm using the global "sName" through the statement: global sName The global statement is only used within functions (def blocks) to indicate that "writes" to the specified name are to modify the MODULE level version of the name, otherwise a write modifies a function local version of the name (you don't need global for read-only access of names, the search for names first looks inside the function, then out to the module) But when I go to use the variable it still gives me an error: NameError: global name 'sName' is not defined I thought perhaps I need to indicate 'globality' in my main module, so before I initiallized sName in doStuff.py I added: global sName But it doesn't help me. I had this issue before and resolved it by declaring the variable global in the sub-module utility.py, but then I needed to reference it in my main module with a prefix: utility.sName = "" It's more verbose,and defining globals in a submodule seems backward. But also, what if I need to access "sName" in another imported module, say "otherstuff.py"? I would do my "import otherstuff" call in my main module, but would I have to put an "import utility" into the otherstuff.py file? If you really need "globals" the common solution is to create a module such as "myglobals", define all the shared names within that module, and import that module where ever you need access to one of the names. And yes, you will need to qualify all those names with the module name (though you can do things like: import myglobals as mg and then use mg.somename instead of myglobals.somename) Thanks for the reply. Good to see that approach has broad support :) I'll do that. I like the idea of a nice short alias for the import to keep the qualifications brief. Ross. -- http://mail.python.org/mailman/listinfo/python-list
