How to tkinter pack_propagate in one direction?

So here's my issue:

I have some class "A" that represents a commonly used format for a tkinter frame. Multiple instances of "A" are stacked on top of each other vertically representing a list of sorts (too complicated for tk.Listbox or Treeview, though). These instances are also supposed to function with a scrollbar, so I placed them in a canvas_frame, which itself is in a canvas, with the appropriate setup. My issue is this: I would like the width of these frames to extend to the edge of the window, however have heights automatically calculated by the usual Tkinter algorithm (however it works). To summarize in code:

'''

import tkinter as tk;
class MyWindow(tk.Tk):
def __init__(self):
super().__init__();
self.title("My Window");
# Setting up main frame on window
self.main_frame = tk.Frame(self.master);
self.main_frame.pack(fill = 'both', expand = True);
self.main_frame.pack_propagate(False);
self.main_frame.configure(width = 500, height = 500);
# Header Frame
self.header = tk.Frame(self.main_frame, height = 50);
self.header.pack(side = 'top', fill = 'both');
self.header.pack_propagate(False);
# Some Header Widgets
self.button1 = tk.Button(self.header, text = "button1");
self.button1.pack(side = 'left');
self.button2 = tk.Button(self.header, text = "button2");
self.button2.pack(side = 'left');
# Body Frame
self.body = tk.Frame(self.main_frame);
self.body.pack(side = 'top', fill = 'both', expand = True);
self.body.pack_propagate(False);
# Scrollable Body Frame Canvas
self.canvas = tk.Canvas(self.body, bg = 'red');
self.canvas.pack(side = 'left', fill = 'both', expand = True);
self.scrollbar = tk.Scrollbar(self.body, command = self.canvas.yview);
self.scrollbar.pack(side = 'right', fill = 'y');
self.canvas.configure(yscrollcommand = self.scrollbar.set);
self.canvas.bind("<Configure>", lambda e: self.canvas.configure(scrollregion = self.canvas.bbox('all')));
self.canvas_frame = tk.Frame(self.canvas);
self.canvas.create_window((0,0), window = self.canvas_frame, anchor = 'nw');
self.item_list = [];
for i in range(10):
self.item_list.append(self.A(self, i));
class A(tk.Frame):
def __init__(self, parent, index):
# Basic Info
self.index = index;
if self.index % 2 == 0:
self.bg_color = 'white';
else:
self.bg_color = 'gray';
super().__init__(parent.canvas_frame, bg = self.bg_color);
self.pack(side = "top", fill = 'both');
self.parent = parent;
self.index = index;
# Sample Widgets
tk.Label(self, text = "Item" + str(self.index) + ", Label1", bg = self.bg_color).pack(side = "top");
tk.Label(self, text = "Item" + str(self.index) + ", Label2", bg = self.bg_color).pack(side = "top");
tk.Label(self, text = "Item" + str(self.index) + ", Label3", bg = self.bg_color).pack(side = "top");
# Plus other widgets...
if __name__ == "__main__":
window = MyWindow()
window.mainloop()

As I stated, my goal is to have each row/"A" frame fill the window/canvas horizontally, but be distributed vertically based on their internal widgets. I belive this is handled by pack_propagate (I may be wrong).

In other words: how do I pack propagate in only one direction?

I tried two solutions:

First is to keep pack_propagate on, but to set the width of the widgets automatically. So within the MyWindow class, I added the following:

self.bind("<Configure>", self.resize);
def resize(self, event):
for item in self.item_list:
item.config(width = event.width);

however when I try this, I think the program ends up in a loop, where each resize changes the width of the frame (due to pack_propagate) and in turn, calls the resize function again.

My second was to turn off pack_propagate, and to try and to do the same thing, but then the height of each "A" instance is 1 and doesn't size automatically.

You can set the width of self.canvas_frame to the width of self.canvas inside the callback of <Configure> event on self.canvas:

class MyWindow(tk.Tk):
    def __init__(self):
        ...
        #self.canvas.bind("<Configure>", lambda e: self.canvas.configure(scrollregion=self.canvas.bbox('all')))

        self.canvas_frame = tk.Frame(self.canvas);
        self.internal = self.canvas.create_window((0,0), window=self.canvas_frame, anchor='nw')

        self.canvas.bind("<Configure>", lambda e: self.canvas.itemconfig(self.internal, width=e.width))
        self.canvas_frame.bind("<Configure>", lambda e: self.canvas.config(scrollregion=self.canvas.bbox("all")))
        ...

Note that scrollregion of the canvas should be updated whenever the internal frame is resized, not the canvas itself.

Also those ; at the end of lines are not necessary.