Tkinter percentage sizes?

Question

I am trying to build a small software with the Tkinter module and python but I can't figure out how to set a widget size with percentages instead of pixels. I could of course do it by grabbing the size of the entire window at every moment and divide by 2 to get a size of 50%, but is there a better way to do it with the Tkinter module?

EDIT 1: To answer your questions I put my code here:

class Navbar:
    def __init__(self, master):
        self.maxsizeFrame = Frame(master, height = 50) #maxsize handler, prevent self.frame to grow too big
        self.maxsizeFrame.pack(fill = X, expand = NO)
        self.frame = Frame(self.maxsizeFrame)
        self.frame.pack(side = TOP, fill = BOTH, expand = YES)
        self.masteries = Button(self.frame, text = "Masteries")
        self.masteries.pack(side = LEFT, fill = BOTH, expand = YES)
        self.runes = Button(self.frame, text = "Runes")
        self.runes.pack(side = RIGHT, fill = BOTH, expand = YES)

So I want to create a navigation bar with two button handled in "self.frame". But I want this design to be responsive, that's why I set expand to "YES". However I wanted to set a maximum size for "self.frame" but the only way I found was to pack this frame in an other one ("self.maxsizeFrame") and set expand to "NO" on this one. And finally, I would like to set the maximum expand size to half the main window, so it could be great if the height of "self.maxsizeframe" could be in percentage. Thanks for reading.

EDIT 2: Actually it seems more efficient to build the software with the grid layout and the weight's option would be accurate.

Answer 1

Ok, I wonder how no one responded yet. So instead of sizing the component at the moment of creation, you can instead use the widget.place() method, define relwidth and relheight (0=0%,0.5=50%,1=100%,etc), this will give the widget x% of its parent width/height. Using place() you can also define relative starting positions for the widgets using relx and rely, and even apply width,height,x, and y by specifying screen units as you would do normally.

Now the fun stuff, which I don't see talked around, is that you can apply relwidth and width at the same time,by playing with negative values and joining relx and x properties, you can get really responsive sites.

Here is an example where I played a bit with this fields to get the responsiveness I've desired:(don't mind 'yposition' comes from the application context)

self.label.place(rely=yposition,x=0.025,relheight=0.04,width=150)   
self.entry.place(rely=yposition,x=150,relheight=0.04,relwidth=0.95,width=-190)
self.button.place(rely=yposition,relx=0.98,x=-40,relheight=0.04,width=40)

Answer 2

If you would like to make it half the size of the window, use width=root.winfo_width / 2, height=winfo_height In the maximum size. (I had to post it late due to the limit of posting per 30Mins