On 15/01/16 08:34, Alan Gauld wrote:
> maybe you can get the mouse positions and put them in order to draw a
> line,etc.
Yes, that's a valid approach to building a multi-segment line.
Normally you store the points in a list somewhere.
> I did not want to use global variable because I am not used to this
> function in python or any lambda function because it's quite hard.
You can avoid lambdas but I think you need to use globals to
get this to work.
You are already using some global variables in your code,
you just need to identify which ones you want to change
in your functions. That's simply done using the global
keyword, so your function would look like:
def some_function(event):
global widget_name
etc...
widget_name = new_value
etc...
It is really quite easy and allows you to store information
from inside a function so that other functions can see it.
The alternative strategy involves creating classes and
objects but that is possibly too advanced for you
just now.
The problem with your existing code is that you are
creating the widgets inside functions. But when the
function ends you lose all references to those widgets
so you cannot modify them or even read them in any
way. (Although the variables all currently refer to
None because you use pack() in the same line as
you create them.)
>> def mouse_position():
>> show_event=app.winfo_pointerxy()
>> (X,Y)=show_event
>> if '<Motion>'!=show_event :
>> show_event=app.winfo_pointerxy()
>> (X,Y)=show_event
>> print("Current mouse are on: X:{0} Y:{1}".format(X,Y))
>> label2=Label(frame1,text=str(show_event),
> relief=GROOVE).pack(side=RIGHT)
>
> And you are right that I have to call the same code to find the
> mouse-position again and again.
Actually you don't really need a function there, I just
realized you can simplify it by just rewriting it as a
single line:
X,Y = app.winfo_pointerxy()
> Then again I don't know what got me but I thought that I could write a
> function for mouse pressed which will print(Right Click has been
> pressed.) and take a variable to store the mouse position. Now I think I
> can modify the code to use separetely to find the coordinates but I
> don't know how to do that. Because in each right click the initialpos
> and finalpos of the mouse will change and they would have the same
> value. Should not they??
Sorry, I'm not sure what you mean there.
Can you try explaining again please?
> If you had tested the code you might have notice that each time I am
> pressing the show button the command keep printing or making a label to
> the right. How do I keep only a single label and delele the old label.
You need to create a global variable and then update that label.
> So any idea how should I store the initial and final position e.g.
> inside a function or as global value.??
Anything that you do in one function that you want to be visible
in another function (or even the same one called a second time)
will need to be stored in a global variable. Variables inside
functions get deleted as soon as the function exits so you cannot
refer to them again. Each time the function gets called it creates
a new set of variables it does not use the same ones as the last
time.
> about mouse position functions? Should I reduce any of them? Is it a
> problem to put labels inside them?
Its OK to create labels inside but they will always be new
labels unless you use global variables.
[Note 1:
Strictly speaking there are some other ways to maintain data
between function calls but I'm pretty sure they are too
esoteric for your purposes. Globals or classes are by far
the simplest solutions
Note 2:
Technically the widgets you are creating do have references
outside the function, otherwise they would be destroyed, but
to reach them involves traversing the app object's containment
tree which is relatively complicated and error prone
]
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor
