fawtytwoCypher | Python Fiddle

from tkinter import *
from tkinter import ttk

def keycheck():
    k = key_entry.get().lower()
    newk = ""
    check = 0
    for i in range(len(k)):
    	if ord(k[i]) in range(97,123):
    		newk += k[i]
            check = 1
    if check == 0:
        return ""
    if check != 0:
        return newk

def encrypt():
    newtext = ""
    text = text_entry.get().lower()
    key = keycheck()
    keycnt = 0
    if key != "":
        for i in range(len(text)):
            if ord(text[i]) in range(97,123): #Checa que esté entre a y z
                if (ord(text[i]) + ord(key[keycnt])- 96 <= 122): #Checa que esté en la primera vuelta
                    newtext += chr(ord(text[i]) + ord(key[keycnt])-96)
                else: #Por si está en la segunda vuelta
                    newtext += chr(ord(text[i]) + ord(key[keycnt])-122)
                keycnt += 1
            else: #Para espacios y otros símbolos
                newtext += text[i]
            if keycnt >= len(key):
                keycnt = 0
        resultText.set(newtext)
    else:
        resultText.set("Key must contain at least one letter")
    
def decrypt():
    newtext = ""
    text = text_entry.get().lower()
    key = keycheck()
    keycnt = 0
    for i in range(len(text)):
        if ord(text[i]) in range(97,123): #Checa que esté entre a y z
            if (ord(text[i]) - ord(key[keycnt])+ 96 >= 97): #Checa que esté en la primera vuelta
                newtext += chr(ord(text[i]) - ord(key[keycnt])+96)
            else: #Por si está en la segunda vuelta
                newtext += chr(ord(text[i]) - ord(key[keycnt])+122)
            keycnt += 1
        else: #Para espacios y otros símbolos
            newtext += text[i]
        if keycnt >= len(key):
            keycnt = 0
    resultText.set(newtext)

#Create Window
root = Tk()
root.title("Cyphering & Decyphering")
#Create widget frame in window
mainframe = ttk.Frame(root, padding="3 3 12 12")
#Create grid in widget, sticky to be used later
mainframe.grid(column=0, row=0)
mainframe.columnconfigure(0, weight=1)
mainframe.rowconfigure(0, weight=1)

#Variable
resultText = StringVar()

#Entries
text_entry = ttk.Entry(mainframe, width= 50)
text_entry.grid(column=1, row=2)
key_entry = ttk.Entry(mainframe, width= 20)
key_entry.grid(column=1, row=4)
resultText_entry = ttk.Entry(mainframe, width= 50, textvariable = resultText)
resultText_entry.grid(column=1, row=9)
resultText_entry.config(state='readonly')

#Labels
ttk.Label(mainframe, text = "Text").grid(column=1, row=1)
ttk.Label(mainframe, text = "Key").grid(column=1, row=3)
ttk.Label(mainframe, text = "Result:").grid(column=1, row=8)
ttk.Label(mainframe, text = "Remember, key must contain one letter").grid(column=1, row=5)

#Buttons
ttk.Button(mainframe, text="Cypher", command= encrypt).grid(column=1, row=6)
ttk.Button(mainframe, text="Decypher", command = decrypt).grid(column=1, row=7)

#For loop adds padding, focus() makes cursor start in Entry
for child in mainframe.winfo_children():
    child.grid_configure(padx=5, pady=5)
text_entry.focus()

root.mainloop()

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