(y1, y2)
return (y2//4 - y1//4) - (y2//100 - y1//100) + (y2//400 - y1//400)
Return number of leap years in range [y1, y2).
       Assume y1 <= y2.
Return number of leap years in range [y1, y2).
       Assume y1 <= y2.
Return number of leap years in range [ y1 y2 ) . Assume y1 < = y2 .
def leapdays(y1, y2):
    """Return number of leap years in range [y1, y2).
       Assume y1 <= y2."""
    y1 -= 1
    y2 -= 1
    return (y2//4 - y1//4) - (y2//100 - y1//100) + (y2//400 - y1//400)
def leapdays ( y1 , y2 ) : y1 -= 1 y2 -= 1 return ( y2 // 4 - y1 // 4 ) - ( y2 // 100 - y1 // 100 ) + ( y2 // 400 - y1 // 400 )