Spaces are used sparingly in expressions. Spaces are never used between a function name and the ()'s that surround the arguments. It is considered poor form to write:

int (22.0/7)

The preferred form is the following:

int(22.0/7)

A long expression may be broken up with spaces to enhance readability. For example, the following separates the multiplication part of the expression from the addition part with a few wisely-chosen spaces.

b**2 - 4*a*c