0:01
Like everything else in Python, functions are objects.
Because functions are objects, we can supply the as arguments in a function
call. Here is a function called
function_runner. It has one perimeter f.
f's type is function. function_runner calls x.
And as you can see in the body, that's exactly what it does.
Here, we define a function that were going to pass the function_runner in just
a little bit. Because this is just a demonstration, all
we'll do inside here is, print that the function was called.
0:53
Every function definition creates a variable with the name of the function
that contains the memory address of a function object that contains all the
details of what it means to run that function when it's called.
[UNKNOWN] happens when we define function 1, then function 2.
Then, we reach the name equals main if statement, and inside that is a call on
function_runner. To execute the function call, we evaluate
the argument. That's just the memory address of the
function object. And then Python creates a frame for the
function. Parameter f is inside that frame.
It is assigned to the memory address of the function that was passed as an
argument. To execute function_runner, we just
execute the statement in its body which is a call on function f.
We draw fame for that function. Were going to write f slash function_1
here, although it turns out that the name of the function is taken from the
function definition. In the body of function_1, we have a call
on function print. That's the end of function_1, so we exit,
that brings us back to function_runner. We've just completed the call on function
f, that's the end of function_runner, so we exit it.
That brings us back to the main program, we're at the end of it, so we exit the
program. When we traced this, we reached one call
on function print. When we run it, we get the output that we
expect. When we change function_1 to function_2,
we see that we end up at this call on function print.
Jennifer CampbellAssociate Professor, Teaching Stream
Paul GriesAssociate Professor, Teaching Stream
