Passing Functions as Arguments

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Из курса от партнера University of Toronto

Learn to Program: Crafting Quality Code

393 оценки

University of Toronto

Learn to Program: Crafting Quality Code

393 оценки

Not all programs are created equal. In this course, we'll focus on writing quality code that runs correctly and efficiently. We'll design, code and validate our programs and learn how to compare programs that are addressing the same task.

Из урока

Week 5

Passing Functions as Arguments2:28

Assigning Parameters Default Values4:19

Dealing with Exceptional Situations 7:26

Познакомьтесь с преподавателями

Jennifer Campbell
Associate Professor, Teaching Stream
Department of Computer Science
Paul Gries
Associate Professor, Teaching Stream
Department of Computer Science

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.

Let's add one more function just like this one.

Here, call function_runner supplying function_1 as the argument.

Now, we'll trace execution of this program.

When the program starts running, we get a frame for the module.

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.

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