from tkinter import *
root = Tk()
root.geometry("300x300")
root.resizable(0, 0)
root.config(bg="#d9ead3")
root.title("Exemplo")

def limpar():
    preco_entrada.delete(0, END)
    quantidade_entrada.delete(0, END)

def app():
    p = preco.get()
    q = quantidade.get()
    ct = p*q
    resultado.set(ct)
preco_texto = Label(text="Preço: ",
                          bg="#d9ead3", fg="#0b5394",
                      font=("Arial", "12", "bold"))
preco_texto.place(relx=0.25, rely=0.2)
preco = DoubleVar()
preco_entrada = Entry(textvariable=preco,
                                  font=("Arial", "12", "bold"),
                                  bg="white", fg="blue", justify='center')
preco_entrada.place(relx=0.5, rely=0.2, relwidth=0.3)

quantidade_texto = Label(text="Quantidade: ",
                          bg="#d9ead3", fg="#0b5394",
                      font=("Arial", "12", "bold"))
quantidade_texto.place(relx=0.1, rely=0.4)
quantidade = DoubleVar()
quantidade_entrada = Entry(textvariable=quantidade,
                                  font=("Arial", "12", "bold"),
                                  bg="white", fg="blue", justify='center')
quantidade_entrada.place(relx=0.5, rely=0.4, relwidth=0.3)
but1 = Button(text="Calcular", bd=2, bg='#107db2', fg='white',
              font=('verdana', 12, 'bold'),command=app)
but1.place(relx=0.15, rely=0.55, relwidth=0.35, relheight=0.1)

but_limpar = Button(text="Limpar", bd=2, bg='#107db2', fg='white',
                    font=('verdana', 12, 'bold'), command=limpar)
but_limpar.place(relx=0.55, rely=0.55, relwidth=0.35, relheight=0.1)
resultado = StringVar()
resulatdoresultado = Label(textvariable=resultado,
                           font=("Arial", 12, "bold"), bg="#f0f8ff")
resulatdoresultado.place(relx=0.6, rely=0.75, relwidth=0.3)

resulatado_texto = Label(text="Custo Total",
                           font=("Arial", 12, "bold"), bg="#d9ead3")
resulatado_texto.place(relx=0.15, rely=0.75, relwidth=0.3)
root.mainloop()