Function Definition: The
def
and
return
Statements
We create a function with a
def
statement. This
provides the name, parameters and the suite of statements that creates the
function's result.
def
name
( 〈
parameter
...〉 ):
suite
The
name
is the name by which the
function is known. The
parameters
is a list of
variable names; these names are the local variables to which actual
argument values will be assigned when the function is applied. The
suite
(which must be indented) is a block of
statements that computes the value for the function.
The first line of a function is expected to be a document string
(generally a triple-quoted string) that provides basic documentation for
the function. This is traditionally divided in two sections, a summary
section of exactly one line and the detail section. We'll return to this
style guide in the section called “Functions Style Notes”.
The
return
statement specifies the result value
of the function. This value will become the result of applying the
function to the argument values. This value is sometimes called the effect
of the function.
Let's look at a complete, although silly, example.
def odd( spin ):
"""Return true if this spin is odd."""
if spin % 2 == 1:
return True
return False
We name this function odd, and define it to
accept a single parameter, named
spin
. We provide a
docstring with a short description of the function. In the body of the
function, we test to see if the remainder of
spin
/2
is 1; if so, we return True. Otherwise, we return
False.
