python expression to latex - python-3.x

Question

I'm trying to display equations by using GUI. I use latex and canvas. However, I'm getting an error message ValueError: KeyPress event keysym=Return keycode=36 char='\r' x=266 y=8
it should be working because I have already converted python expressions into Latex's.
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg
import matplotlib
import matplotlib.pyplot as plt
from tkinter import *
from sympy import *
matplotlib.use('TkAgg')
root=Tk()
frame=Frame(root)
frame.pack()
frame1= Frame()
frame1.pack()
caracter=StringVar()
def result(caracter):
a = str(caracter)
text1=latex(a)
ax.clear()
ax.text(0.2, 0.6, "$"+text1+"$", fontsize = 6)
canvas.draw()
def element(num):
caracter.set(caracter.get()+num)
#-----------------------------SCREEN------------
screen=Entry(frame, width=50, textvariable=caracter)
screen.pack()
screen.grid(row=1, column=1, pady=10, columnspan=5)
#-----------------------BUTTONS-----------------------
go=Button(frame, height=1, text="Go")
go.grid(row=1, column=6)
Buttonx=Button(frame, text="x", width=5, padx=0, pady=2, command=lambda:element("x"))
Buttonx.grid(row=2, column=6)
#--------CANVAS ---------------
label = Label(frame1)
label.pack()
fig = matplotlib.figure.Figure(figsize=(5, 4), dpi=100)
ax = fig.add_subplot(111)
canvas = FigureCanvasTkAgg(fig, master=label)
canvas.get_tk_widget().pack(side=TOP, fill=BOTH, expand=1)
canvas._tkcanvas.pack(side=TOP, fill=BOTH, expand=1)
ax.get_xaxis().set_visible(False)
ax.get_yaxis().set_visible(False)
root.bind('<Return>', result)
root.mainloop()
This is the shortest code to reproduce the issue. Any help or hint will be appreciated. Thank you very much in advance

Answer 1

You are passing the char associated with <RETURN> to your function result. Because the parameter is named caracter, this shadows the variable caracter declared earlier as a tk.StringVar.
something like this should give you the expected result:
def result(dummy_c):
a = caracter.get()
text1 = latex(a)
ax.clear()
ax.text(0.2, 0.6, "$"+text1+"$", fontsize = 6)
canvas.draw()