IS there a way to simplify this python code?

I am still in the "any technology sufficiently advanced..." phase of learning to program. This code seems clunky, and hard to update if needed. Is there a better way to go about this? It just looks completely bonkers to me, but it works... so yay?

It takes a variable from TKinter radial 1-16, and uses it select the grade1 ect variable. The grade1 variable then link to sheet names on gspread.

def go():
    subject = v.get()
    if  subject == 1:
        subject = grade1
    elif  subject == 2:
        subject = grade2    
    elif  subject == 3:
        subject = grade3
    elif  subject == 4:
        subject = grade4  
    elif  subject == 5:
        subject = grade5
    elif  subject == 6:
        subject = grade6
    elif  subject == 7:
        subject = grade7
    elif  subject == 8:
        subject = grade8
    elif  subject == 9:
        subject = grade9
    elif  subject == 10:
        subject = grade10    
    elif  subject == 11:
        subject = grade11
    elif  subject == 12:
        subject = grade12 
    elif  subject == 13:
        subject = grade13
    elif  subject == 14:
        subject = grade14
    elif  subject == 15:
        subject = grade15
    elif  subject == 16:
        subject = grade16