# ===================================================================
# layout With Frames and Grids
# ===================================================================
# Frames contain their own 'grid space'.
#
# As a general rule of thumb you should never call grid, pack or
# place as part of the same statement that creates the widget.
# Partially it is for this exact behavior that you're experiencing,
# but also because I think it makes your code harder to write and
# harder to maintain over time.
#
# Widget creation and widget layout are two different things. In my
# experience, layout problems are considerably easier to debug when
# you group your layout commands together.
#
# Also, you should be consistent when using grid and always put
# the options in the same order so you can more easily visualize
# the layout. And finally, when using grid you should get in the
# habit of always specifying the sticky option, and always give
# one row and one column in each containing frame a non-zero weight.
#
# -------------------------------------------------------------------
# Note the following:
#
# top_frame = Frame(root, ...).grid(row=0, ...)
#
# In python, x = y().z() will always set x to the result of .z() .
# In the case of top_frame = Frame(...).grid(...), grid(...) always
# returns None so top_frame will be None. That causes every widget
# that you think is going into the top frame to actually go in the
# root window.
# -------------------------------------------------------------------
# from: stackoverflow.com/questions/34276663/
# tkinter-gui-layout-using-frames-and-grid
# ===================================================================
from Tkinter import *
root = Tk()
root.title('Model Definition')
root.geometry('{}x{}'.format(460, 350))
# create all of the main containers
top_frame = Frame(root, bg='cyan', width=450, height=50, pady=3)
center = Frame(root, bg='gray2', width=50, height=40, padx=3, pady=3)
btm_frame = Frame(root, bg='white', width=450, height=45, pady=3)
btm_frame2 = Frame(root, bg='lavender', width=450, height=60, pady=3)
# layout all of the main containers
root.grid_rowconfigure(1, weight=1)
root.grid_columnconfigure(0, weight=1)
top_frame.grid(row=0, sticky="ew")
center.grid(row=1, sticky="nsew")
btm_frame.grid(row=3, sticky="ew")
btm_frame2.grid(row=4, sticky="ew")
# create the widgets for the top frame
model_label = Label(top_frame, text='Model Dimensions')
width_label = Label(top_frame, text='Width:')
length_label = Label(top_frame, text='Length:')
entry_W = Entry(top_frame, background="pink")
entry_L = Entry(top_frame, background="orange")
# layout the widgets in the top frame
model_label.grid(row=0, columnspan=3)
width_label.grid(row=1, column=0)
length_label.grid(row=1, column=2)
entry_W.grid(row=1, column=1)
entry_L.grid(row=1, column=3)
# create the center widgets
center.grid_rowconfigure(0, weight=1)
center.grid_columnconfigure(1, weight=1)
ctr_left = Frame(center, bg='blue', width=100, height=190)
ctr_mid = Frame(center, bg='yellow', width=250, height=190, padx=3, pady=3)
ctr_right = Frame(center, bg='green', width=100, height=190, padx=3, pady=3)
ctr_left.grid(row=0, column=0, sticky="ns")
ctr_mid.grid(row=0, column=1, sticky="nsew")
ctr_right.grid(row=0, column=2, sticky="ns")
root.mainloop()