# Tk_basic_calc_demo.py

 # -*- coding: utf-8 -*-
# Tk_basic_calc_demo.py

from Tkinter import *
import tkFont

#ACTIONS
def clear():
    #Action: Clears the entry()
    txtDisplay.delete(0,END)
    return

ERROR='< ERROR >'
def update_Entry(inputValue):
    #Updates the entry when a button is pressed
    currentText=num1.get()
    currentText=currentText.replace(ERROR,'')
    update=num1.set(currentText + inputValue)

def evaluate():
    currentText=num1.get()
    currentText=currentText+'*1.0'
    try:
        num1.set(str(eval(currentText)))
    except:
        num1.set(ERROR)

#Parent Window
root=Tk()
root.title('Basic Calculator')
# root.geometry('100x100')

#Main entry
num1=StringVar()
displayFont = ('Verdana',21)
txtDisplay=Entry(root, textvariable=num1, relief=RIDGE, bd=3, insertwidth=1, font=displayFont, justify=RIGHT)
txtDisplay.place(x=12, y=16)
txtDisplay.place(width=310, height=40)
txtDisplay.focus()

print(txtDisplay.get())

#Pseudo y-axis padding
ppad=10
y1=65;y2=105+(ppad);y3=145+(ppad*2);y4=185+(ppad*3);y5=225+(ppad*4)

default_font=tkFont.nametofont('TkDefaultFont')
default_font.configure(family='Tahoma', size=16, weight='bold')

#Buttons : Note '/' equals '÷'
zeroButton=Button(root, text='0', width=11, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('0'))
zeroButton.place(x=12,y=y5)
oneButton=Button(root, text='1', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('1'))
oneButton.place(x=12, y=y4)
twoButton=Button(root, text='2', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('2'))
twoButton.place(x=90, y=y4)
threeButton=Button(root, text='3', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('3'))
threeButton.place(x=168, y=y4)
fourButton=Button(root, text='4', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('4'))
fourButton.place(x=12, y=y3)
fiveButton=Button(root, text='5', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('5'))
fiveButton.place(x=90, y=y3)
sixButton=Button(root, text='6', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('6'))
sixButton.place(x=168, y=y3)
sevenButton=Button(root, text='7', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('7'))
sevenButton.place(x=12, y=y2)
eightButton=Button(root, text='8', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('8'))
eightButton.place(x=90, y=y2)
ninthButton=Button(root, text='9', width=5, height=0, bg='LightBlue', fg='red', command=lambda:update_Entry('9'))
ninthButton.place(x=168, y=y2)

decimalButton=Button(root, text='.', width=5, height=0, bg='powder blue', command=lambda:update_Entry('.'))
decimalButton.place(x=168, y=y5)
plusButton=Button(root, text='+', width=5, height=0, bg='gray', command=lambda:update_Entry('+'))
plusButton.place(x=246, y=y3)
minusButton=Button(root, text='-', width=5, height=0, bg='gray', command=lambda:update_Entry('-'))
minusButton.place(x=246, y=y2)
multiplyButton=Button(root, text='x', width=5, height=0, bg='gray', command=lambda:update_Entry('*'))
multiplyButton.place(x=246, y=y1)
divideButton=Button(root, text='÷', width=5, height=0, bg='gray', command=lambda:update_Entry('/'))
divideButton.place(x=168, y=y1)
clearButton=Button(root, text='Clear (CE)', width=11, height=0, command=clear, bg='Orange')
clearButton.place(x=12, y=y1)
equalButton=Button(root, text='=', width=5, height=3, bg='Lightgreen', command=lambda:evaluate())
equalButton.place(x=246, y=y4)

#Locks the parent windows size
root.maxsize(334,340)
root.minsize(334,340)

#Parent window's background color
root.configure(background='blue')
root.mainloop()