#   - is left associative
9 - 3 - 1
#   a parenthesis is needed if the right - is required to be executed first
9 - (3 - 1)
#   * has higher precedence than + or 1.
4 + 2 * 5 - 6
#   //, / and * are left associative.
6 // 4 / 2
#   //, / and * are left associative.
4 * 8 // 5
#   () is needed with the right // should be executed first. It returns a different result.
4 * (8 // 5)
#  ** is right associative
2 ** 3 ** 2
#   () is needed if the left ** should be executed first.
(2 ** 3) ** 2
#   bitwise left shift is left associative.
6 >> 3 >> 1
#  a pair of parentheis is need if the right >> should be executed first.
6 >> (3 >> 1)
#   comparison operators have a higher precedence than relational operators. and has a higher precedence than or.
1 < 2 or 3 < 4 and 4 > 6
(1 < 2 or 3 < 4) and 4 > 6
1 < 2 or (3 < 4 and 4 > 6)