Our first functions

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From the course by Wesleyan University

Python Programming: A Concise Introduction

1567 ratings

Wesleyan University

Python Programming: A Concise Introduction

1567 ratings

The goal of the course is to introduce students to Python Version 3.x programming using hands on instruction. It will show how to install Python and use the Spyder IDE (Integrated Development Environment) for writing and debugging programs. The approach will be to present an example followed by a small exercise where the learner tries something similar to solidify a concept. At the end of each module there will be an exercise where the student is required to write simple programs and submit them for grading. It is intended for students with little or no programming background, although students with such a background should be able to move forward at their preferred pace. The course is four modules long and is designed to be completed in four weeks.

From the lesson

Beginning to Program in Python

In this module we introduce writing functions in Python using the convenient Spyder development environment. The lesson begins with instructions on installing the popular Anaconda distribution of Python, which includes Spyder. It continues by showing how to use the editor in Spyder to type in a function and then run it. Each lesson alternates between introducing a concept by example and having the student test his/her understanding by constructing a function similar to that example. The module lecture is contained in a single program source file named Exercises1.py. This file, which should be downloaded by the student at the beginning of the module, contains the complete lecture except the solutions to the ungraded exercises. The student should work each of these before viewing the instructor's solution. By using the unique capability of Spyder (using IPython Notebooks), the program file is segmented into cells each of which can be executed independently of the others. Thus the student does not have to manage multiple program files and finishes with a lecture file with filled-in student exercises that can be used for reference. Python topics included in this module are print statement, arithmetic operators, input statement, combining of strings, if statement, while loop, and for loop. The module ends with a series of small functions to write to be submitted for grading. Grading is done by custom software and should normally take only minutes with no limit to the number of re-submissions. Hopefully, you'll finish with a perfect score.

Introduction to the Spyder IDE10:30

Arithmetic operations1:07

Our first functions4:41

Meet the Instructors

Bill Boyd
Visiting Associate Professor and Visiting Scholar
Quantitative Analysis Center

Now let's look at a simple function in Python.

The kernel that we have, percent, pound percent sent, and

pound percent sent, and they mark out a cell.

These lines show you the boundaries of the cell.

Here we have a function defined within a cell, and

we can execute that by typing Ctrl, Enter.

On a Macintosh it would be command return.

Now this function can be run by

typing in the console the name of the function.

Hello, world!

A couple of things to note about this.

One is it's got a single statement.

Print hello world.

And it does that.

And this statement is indented four spaces, one, two, three, four.

We always indent four spaces we don't use tabs that can sometimes cause

confusion on the part of python.

I've also got a string here enclosed in triple quotes.

This string can be used to document the program, and

if you notice up here in [INAUDIBLE] inspector,

you can get the definitions of various functions and

we can get the definition of our function by clicking on hello.

Yeah, I'm here type in control I.

Then our function shows up here in this triple queried string is a documentation

so that you can put instructions on how to run your program for example in that or

your function.

Now let's write another function.

Here's the area of a circle of a given radius.

Again we've got pound percent cent to mark out the cell.

We can execute this [INAUDIBLE] anywhere in the cell and

type in control enter or command return on a Macintosh.

That puts, that loads it into the console window over here.

And now we can run it by typing, Area of a circle, the name of the function.

And I'll give it a value of five for the radius.

It prints out the area of a circle of radius 5 is 78.5.

Now let's look at does that first of all,

we have the formula for the area of a circle.

Area is equal to pi, 3.14 times the radius, squared.

Just a simple formula for the area of a circle.

Now, we print the phrase, the area of a circle of radius,

all about the radius is all about the area that we computed.

Now you try writing a function, here is an exercise to do.

Write a function def area triangle BH where B is the base and H

is the height of the triangle, to compute the area of a triangle the formula is area

equals one half base times the height, output should look like the following.

The area of a triangle of base 3 and height 5 is 7 and a half.

You can test your function by executing the following code.

Here's a triangle of base 3 and height 5,

here's one of base 2 and height 20.

Here is my run of this.

The area of a triangle of base 3 and height 5 is 7.5.

The area of a triangle of base 2 and height 20 is 20.

Now you try it, when you get through, press continue and

I'll show you my solution.

Okay, here is my solution.

Definition area of triangle,

bh is area equal one-half base times the height, just that same formula.

Print the area of a triangle of base, b, and height h, is area.

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