Core Python Programming (2nd Edition)

additional non-keyword arg: 30
additional non-keyword arg: 40
additional keyword arg 'foo': 50
additional keyword arg 'bar': 60
We will now make a similar call; however, instead of listing the variable arguments individually, we will
put the non-keyword arguments in a tuple and the keyword arguments in a dictionary to make the call:
>>> newfoo(2, 4, *(6, 8), **{'foo': 10, 'bar': 12})
arg1 is: 2
arg2 is: 4
additional non-keyword arg: 6
additional non-keyword arg: 8
additional keyword arg 'foo': 10
additional keyword arg 'bar': 12
Finally, we will make another call but build our tuple and dictionary outside of the function invocation:
>>> aTuple = (6, 7, 8)
>>> aDict = {'z': 9}
>>> newfoo(1, 2, 3, x=4, y=5, *aTuple, **aDict)
arg1 is: 1
arg2 is: 2
additional non-keyword arg: 3
additional non-keyword arg: 6
additional non-keyword arg: 7
additional non-keyword arg: 8
additional keyword arg 'z': 9
additional keyword arg 'x': 4
additional keyword arg 'y': 5
Notice how our tuple and dictionary arguments make only a subset of the final tuple and dictionary
received within the function call. The additional non-keyword value '3' and keyword pairs for 'x' and
'y' were also included in the final argument lists even though they were not part of the '*' and '**'
variable argument parameters.
Prior to 1.6, variable objects could only be passed to apply() with the function object for invocation. This
current calling syntax effectively obsoletes the use of apply(). Below is an example of using these
symbols to call any function object with any type of parameter set.
Functional Programming Example
Another useful application of functional programming comes in terms of debugging or performance
measurement. You are working on functions that need to be fully tested or run through regressions
every night, or that need to be timed over many iterations for potential improvements. All you need to
do is to create a diagnostic function that sets up the test environment, then calls the function in
question. Because this system should be flexible, you want to allow the testee function to be passed in
as an argument. So a pair of such functions, timeit() and testit(), would probably be useful to the
software developer today.
We will now present the source code to one such example of a testit() function (see Example 11.5).