Python in a Nutshell

Numeric Operations

Python supplies the usual numeric operations, as you’ve just seen in Table 4-2. All numbers are immutable objects, so when you perform a numeric operation on a number object, you always produce a new number object. You can access the parts of a complex object z as read-only attributes z.real and z.imag. Trying to rebind these attributes on a complex object raises an exception.

Note that a number’s optional + or - sign, and the + that joins a floating-point literal to an imaginary one to make a complex number, are not part of the literals’ syntax. They are ordinary operators, subject to normal operator precedence rules (see Table 4-2). This is why, for example, -2**2 evaluates to -4: exponentiation has higher precedence than unary minus, so the whole expression parses as -(2**2), not as (-2)**2.

Coercion and Conversions

You can perform arithmetic operations and comparisons between any two numbers. If the operands’ types differ, coercion applies: Python converts the operand with the smaller type to the larger type. The types, in order from smallest to largest, are integers, long integers, floating-point numbers, and complex numbers.

You can also perform an explicit conversion by passing a numeric argument to any of the built-ins: int, long, float, and complex. int and long drop their argument’s fractional part, if any (e.g., int(9.8) is 9). Converting from a complex number to any other numeric type drops the imaginary part. You can also call complex with two arguments, ...