Open interval means the two values at the boundaries of the interval are not included, the format is:
(a, b)

Equivalent to:

a < x < b
Closed interval means the two values at the boundaries of the interval are included, the format is:
[a,b]

Equivalent to:

a <= x <=b
Half-open interval means the boundary value on the open interval side is not included, while the boundary value on the closed interval side is included, the format is:
[a,b)  # 取值包括 a，但不包括 b
或
(a,b]  # 取值不包括 a，但包括 b

Equivalent to:

a <= x < b
或
a < x <=b