分配2之前引用的局部变量

Question

I'm a Python beginner trying the tkinter library. I am trying to create two text boxes: one will ask for hours and the other for the hourly rate. These values will be multiplied. If the hourly rate is more than 40, it will multiply the hours above 40 by 1.5 to reflect the overtime rate. I get an error:

UnboundLocalError: local variable 'salary' referenced before assignment

I am not sure if this is the only error in my code. How can I resolve this error?

from tkinter import  *
from tkinter  import ttk

def main():
    value = float(hours.get())
    value2=float(rate.get())
    salary.set(value * value2)
    if hours > 40 : 
        salary = (((hours - 40)* 1.5 ) + 40 )* rate 
    else : 
        salary = hours * rate 
    return salary 

root = Tk()
root.title = ("Salary Calculator")

hours = StringVar()
rate = StringVar()
salary = StringVar()


entry = Entry(root, textvariable=hours)
entry2 = Entry(root, textvariable=rate)
label1=Label(root,textvariable=salary)
label2=Label(root, text='Enter Your Hours Worked: ')
button1=Button(root,text='Calculate Salary',command=main)


entry.pack()
entry2.pack()
label1.pack()
button1.pack()
label2.pack()


root.mainloop()

Answer 1

You don't assign salary before you use it in the local scope:

 salary.set(value * value2) # <- not defined

You set it in the if statements after you have already tried to use it, you are shadowing the salary = StringVar() in the local scope:

 if hours > 40 :
        salary = (((hours - 40)* 1.5 ) + 40 )* rate # shadows the global salary
    else :
        salary = hours * rate
    return salary

I think you want something more like, which will not cause an error and update the label correctly, you are currently trying to compare StringVar's and and ints:

def main():
    value = float(hours.get())
    value2 = float(rate.get())
    if value > 40 : # compare to .get float not StringVar
        val= (((value - 40)* 1.5 ) + 40 )* value2
    else :
        val = value * value2
    salary.set(val) # set after to whatever val is
    return val