Module 1: Your First Program

• First read this page then start coding the module.
• Post your Python files to Blackboard under the module 1 assignment.

Objectives

Experience writing a really simple program.

Hello World in Python

Here is the classic Hello World program in Python:

hello.py

print("Hello World!")

This is a simple program written in the Python programming language, possibly one of the smallest programs one can write, and a traditional starting point for learning programming.

Let’s point out a few things:

• What we see above is the text of the program.
  • The sequence of letters `print(“Hello World!”) is the program
  • When you type it in, it may look different (in color, fonts), and that’s fine
• The entire program will appear inside of a code editor when we write.
• We could use one of several code editors.
• This is how it would look inside the Thonny code editor:

• Various editors colorize in different ways for convenience of reading, none of which affect the actual text of the program.

• Apart from typing it in, you have to run the program.

• Intuitively, just looking at the program we might think that:
  • It has to do with some kind of “printing” because we see print
• There are several ways to run a program:
  • Run the program inside the very same editor used to type the program.
  • Run it without any editor.

• In Thonny you can press the green “play” button to run the program.

• The result of any printing appears in the shell tab.

• Try this yourself.

• Save the program as hello.py.

• Later we will attach this file to your assignment submission on Blackboard.

What’s with printing the phrase “Hello World!”

It’s a tradition in computer science that your first program will print “Hello World!”

It’s meant to pretend that a program is a creature that’s itself communicating to the outside world by saying hello.

Hello World Variation

We will now spend a bit of time trying a few variations, and also examining what happens when typing mistakes are made.

Consider this program:

helloname.py

print("Hello World!")
print("My name is X")

• Open a new file in the Thonny editor.

• Type up this program but use your own name instead of X.

• Run the program.

• Save the program as helloname.py.

• Later we will attach this file to your assignment submission on Blackboard.

What happens when things go (even slightly) wrong

We’ll now deliberately make a few tiny errors and see what happens:

Error #1: forgetting to type the closing parenthesis.

error1.py

print("Hello World!"

Note the missing right parenthesis at the end of the line.

• What happens when we nonetheless try and run the program?

• Run the program.

• Save the program as error2.py.

• Later we will attach this file to your assignment submission on Blackboard.

Error #2: What happens if we forget the quotation marks?

error2.py

print(Hello World!)

• What happens when we nonetheless try and run the program?

• Run the program.

• Save the program as error2.py.

• Later we will attach this file to your assignment submission on Blackboard.

Submission Instructions

Attach the files hello.py, helloname.py, error1.py, and error2.py to the Module 1 assignment on blackboard and submit the assignment.