Multiple Function Arguments

Tutorial

Every function in Python receives a predefined number of arguments, if declared normally, like this:

def myfunction(first, second, third):
    # do something with the 3 variables
    ...

It is possible to declare functions which receive a variable number of arguments, using the following syntax:

def foo(first, second, third, *therest):
    print "First: %s" % first
    print "Second: %s" % second
    print "Third: %s" % third
    print "And all the rest... %s" % list(therest)

The "therest" variable is a list of variables, which receives all arguments which were given to the "foo" function after the first 3 arguments. So calling foo(1,2,3,4,5) will print out:

First: 1
Second: 2
Third: 3
And all the rest... [4, 5]

It is also possible to send functions arguments by keyword, so that the order of the argument does not matter, using the following syntax:

def bar(first, second, third, **options):
    if options.get("action") == "sum":
        print "The sum is: %d" % (first + second + third)

    if options.get("return") == "first":
        return first

...

result = bar(1, 2, 3, action = "sum", return = "first")
print "Result: %d" % result

The following code yields the following output:

The sum is: 6
Result: 1

The "bar" function receives 3 arguments. If an additional "action" argument is received, and it instructs on summing up the numbers, then the sum is printed out. Alternatively, the function also knows it must return the first argument, if a "return" argument is received which instructs it.

Exercise

Fill in the "foo" and "bar" functions so they can receive a variable amount of arguments (3 or more) The "foo" function must return the amount of extra arguments received. The "bar" must return "True" if the argument with the keyword "magicnumber" is worth 7, and False otherwise.

Tutorial Code

# edit the functions prototype and implementation
def foo(a, b, c):
    pass

def bar(a, b, c):
    pass

# test code
if foo(1,2,3,4) == 1:
    print "Good."
if foo(1,2,3,4,5) == 2:
    print "Better."
if bar(1,2,3,magicnumber = 6) == False:
    print "Great."
if bar(1,2,3,magicnumber = 7) == True:
    print "Awesome!"

Expected Output

Good.
Better.
Great.
Awesome!

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