import tkinter as tk

class Calculator:
    def __init__(self, root):
        self.root = root
        self.root.title("Calculator")
        self.expression = ""
        
        # Create display field
        self.display = tk.Entry(root, font=("Arial", 20), bd=10, insertwidth=2, width=14, borderwidth=4, bg="lightgrey")
        self.display.grid(row=0, column=0, columnspan=4, pady=10)
        
        # Create buttons
        buttons = [
            '7', '8', '9', '+',
            '4', '5', '6', '-',
            '1', '2', '3', '=',
            'C', '0'
        ]
        
        row_val = 1
        col_val = 0
        for button in buttons:
            if button == "=":
                tk.Button(root, text=button, padx=20, pady=20, font=("Arial", 18), command=self.calculate).grid(row=row_val, column=col_val, columnspan=2, pady=5)
                col_val += 2
            elif button == "C":
                tk.Button(root, text=button, padx=20, pady=20, font=("Arial", 18), command=lambda b=button: self.on_button_click(b)).grid(row=row_val + 1, column=0, pady=5)
            elif button == "0":
                tk.Button(root, text=button, padx=20, pady=20, font=("Arial", 18), command=lambda b=button: self.on_button_click(b)).grid(row=row_val + 1, column=1, pady=5)
                col_val += 1
                if col_val > 3:
                    col_val = 0
                    row_val += 1
            else:
                tk.Button(root, text=button, padx=20, pady=20, font=("Arial", 18), command=lambda b=button: self.on_button_click(b)).grid(row=row_val, column=col_val, pady=5)
                col_val += 1
                if col_val > 3:
                    col_val = 0
                    row_val += 1

    def on_button_click(self, char):
        if char == "C":
            self.expression = ""
        else:
            self.expression += str(char)
        self.display.delete(0, tk.END)
        self.display.insert(tk.END, self.expression)

    def calculate(self):
        try:
            result = str(eval(self.expression))
            self.display.delete(0, tk.END)
            self.display.insert(tk.END, result)
            self.expression = result
        except:
            self.display.delete(0, tk.END)
            self.display.insert(tk.END, "Error")
            self.expression = ""

if __name__ == "__main__":
    root = tk.Tk()
    calc = Calculator(root)
    root.mainloop()