Question

I am trying to build a GUI calculation in Python but I keep getting this error message that "self" is not defined. Is anyone familiar with the work on this? Please assist. I will attach my code below.

Answer 1

from tkinter import *
root = Tk()

class Calc():
def __init__(self, parent=None):
'calculator constructor'
Frame.__init__(self, parent)
self.pack()

self.memory = '' # memory
self.expr = '' # current expression
self.startOfNextOperand = True

def click(self, key):
'handler for event of pressing button labeled key'

if key == '=':
# evaluate the expression, including the value
# displayed in entry and display result
try:
result = eval(self.expr + self.entry.get())
self.entry.delete(0, END)
self.entry.insert(END, result)
self.expr = ''
except:
self.entry.delete(0, END)
self.entry.insert(END, 'Error')

elif key in '+*-/':
# add operand displayed in entry and operator key
# to expression and prepare for next operand
self.expr += self.entry.get()
self.expr += key
self.startOfNextOperand = True

elif key == '\u221a':
# compute and display square root of entry
result = sqrt(eval(self.entry.get()))
self.entry.delete(0, END)
self.entry.insert(END, result)

elif key == 'x\u00b2':
# compute and display the square of entry
result = eval(self.entry.get())**2
self.entry.delete(0, END)
self.entry.insert(END, result)

elif key == 'C': # clear entry
self.entry.delete(0, END)

elif key in {'M+', 'M-'}:
# add or subtract entry value from memory
self.memory = str(eval(self.memory+key[1]+self.entry.get()))

elif key == 'MR':
# replace value in entry with value stored in memory
self.entry.delete(0, END)
self.entry.insert(END, self.memory)

elif key == 'MC': # clear memory
self.memory = ''

elif key == '+-':
# switch entry from positive to negative or vice versa
# if there is no value in entry, do nothing
try:
if self.entry.get()[0] == '-':
self.entry.delete(0)
else:
self.entry.insert(0, '-')
except IndexError:
pass
else:
# insert digit at end of entry, or as the first
# figit if start of next operand
if self.startOfNextOperand:
self.entry.delete(0, END)
self.startOfNextOperand = False
self.entry.insert(END, key)


buttons = [['MC', 'M+', 'M-', 'MR'],
['C' , '\u221a', 'x\u00b2', '+' ],
['7' , '8' , '9' , '-' ],
['4' , '5' , '6' , '*' ],
['1' , '2' , '3' , '/' ],
['0' , '.' , '+-', '=' ]]

# use Entry widget for display
self.entry = Entry(self, relief=RIDGE, borderwidth=3,
width=20, bg='gray',
font=('Helvetica', 18))
self.entry.grid(row=0, column=0, columnspan=5)

# create and place buttons in appropriate row and column
for r in range(6):
for c in range(4):

# function cmd() is defined so that when it is
# called without an input argument, it executes
# self.click(buttons[r][c])
def cmd(x=buttons[r][c]):
self.click(x)

b = Button(self, # button for symbol buttons[r][c]
text=buttons[r][c],
width=3,
relief=RAISED,
command=cmd) # cmd() is the handler
b.grid(row=r+1, column=c) # entry is in row 0

root.mainloop()

Answer 2

I see a number of things that I'm suspicious of, but self not being defined I'd guess is because Calc is never instantiated.

Answer 3

How can i do this? @rsmith6559

Answer 4

It would probably need to be done in the main part of the program, before the mainloop. I don't know if this code is copied, or your own design, so I'm not sure where to put it.

Answer 5

The spacing makes it a bit hard to debug but it looks like everything from the line
"buttons = [['MC', 'M+', 'M-', 'MR']," on is outside the class definition. Using self will cause errors because self is not defined outside the scope of the class.
I tried to copy and paste it into my editor but it all got put on one line. I know on some other sites they have special ways to post code. Not sure how it can be done here.

Answer 6

I believe it's between triple back ticks (lowercase ~).