Python, Tkinter: NameError: global name 'Combobox' is not defined

I have created a combobox for my gui application in Python but I have been getting this error when declaring my combobox in my init function: `TypeError: 'Combobox' object is not callable` Here is the code I am using for this: ``` class ProgramingPractice(Tk): def __init__(self): super(ProgramingPractice, self).__init__() self.variableCombo_value = StringVar() self.variableCombo = ttk.Combobox() def questionVariables(self): self.variableCombo_value = StringVar() self.variableCombo(self.formSize, textvariable = self.variableCombo, state = 'readonly') self.variableCombo['values'] = ('Month', 'Year', 'Age', 'Day') self.variableCombo.pack() ``` I have tried different solutions to this problem but I have either got an Attibute error or a name error. Does anyone know of a solution to this problem? This is the smallest I can make the code while still getting the error: ``` import sys from tkinter import * from tkinter import ttk class ProgramingPractice(Tk): def __init__(self): super(ProgramingPractice, self).__init__() self.formSize() self.variableCombo_value = StringVar() self.variableCombo = ttk.Combobox() def formSize(self): self.geometry("700x450+200+200") # Sets the size of the gui def questionVariables(self): self.variableCombo_value = StringVar() self.variableCombo.configure(self.formSize, textvariable = self.variableCombo_value, state = 'readonly') self.variableCombo['values'] = ('Month', 'Year', 'Age', 'Day') self.variableCombo.pack() pp = ProgramingPractice() pp.questionVariables() ```