Converting Total Seconds to Minutes and Seconds

def mile_pace(miles, duration):

#capturing the minutes from the string thereby converting into int type
   
    #[0:-3] from the 0th to 4th last index
    minutes=int(duration[0:-3]) 
    #[-2:0] from the 2nd last to last index
    seconds=int(duration[-2:]) 
    
    average=(minutes*60+seconds)/(miles) #in seconds/miles
#1minute=60seconds #converting seconds>60 to minutes and seconds
    if average>60:  
#quotient=average//60=>minutes part
        whole_part=average//60 
    
#remainder=average//60=>minutes part
        decimal_part=average%60
        
#conditions for padding extra zeros to minutes and seconds strings
    if int(whole_part)>=10 and int(decimal_part)>=10: duration=str(int(whole_part))+":"+str(int(decimal_part))
    
    elif int(whole_part)<10 and int(decimal_part)<10: duration="0"+str(int(whole_part))+":0"+str(int(decimal_part))
    
    elif int(whole_part)<10 and int(decimal_part)>=10: duration="0"+str(int(whole_part))+":"+str(int(decimal_part))
    
    elif int(whole_part)>=10 and int(decimal_part)<10: duration=str(int(whole_part))+":0"+str(int(decimal_part))
    
    return duration