Python Language Reference Manual by Guido van Rossum and Fred L. Drake, Jr. Paperback (6"x9"), 120 pages ISBN 0954161785 RRP £12.95 ($19.95) Sales of this book support the Python Software Foundation! Get a printed copy>>> 
5.5 Unary arithmetic operations
All unary arithmetic (and bitwise) operations have the same priority:
u_expr
power

 ""
u_expr
 "+"u_expr
 "~"u_expr
The unary 
(minus) operator yields the negation of its
numeric argument.
The unary +
(plus) operator yields its numeric argument
unchanged.
The unary ~
(invert) operator yields the bitwise inversion
of its plain or long integer argument. The bitwise inversion of
x
is defined as (x+1)
. It only applies to integral
numbers.
In all three cases, if the argument does not have the proper type,
a TypeError
exception is raised.
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