import tkinter as tk
from tkinter import ttk


class Main(tk.Tk):  # create a class, that is inherited from tk.Tk
    def __init__(self):  # create __init__ method. It's called when the Main object is created
        super().__init__()  # add all tk.Tk's methods and attributes to this class

        self.title("Buscador de Codigos")

        self.frame1 = ttk.Frame(self)
        self.buscar_entry = tk.Entry(self.frame1)
        self.buscar_button = ttk.Button(self.frame1, text="Buscar")

        self.frame2 = ttk.Frame(self)
        self.treeview = ttk.Treeview(self.frame2, columns=("codigo", "desc"))

        self.treeview.heading("#0", text="Renglon")
        self.treeview.column("#0", minwidth=85, width=85)
        self.treeview.heading("codigo", text="Codigo SIGES")
        self.treeview.column("codigo", minwidth=85, width=85)
        self.treeview.heading("desc", text="Descripción")
        self.treeview.column("desc", minwidth=600, width=600)

        self.frame1.pack(fill="x", padx=10, pady=(10, 0))
        self.buscar_entry.pack(fill="x", expand=True, side="left")  # expand=False is a default value, so I have removed this arg
        self.buscar_button.pack(side="left", padx=(10, 0))
        self.frame2.pack(fill="both", expand=True, padx=10, pady=10)
        self.treeview.pack(fill="both", expand=True, side="bottom")

if __name__ == "__main__":  # if this file is imported, nothing happens
    root = Main()  # create a Main object
    root.mainloop()  # start the mainloop

    # Or even: Main().mainloop()