print("hi")

A First Program

• "Hello world!" is traditionally the first program you write when learning a new language
• simply outputs "Hello world!"

Follow these steps:

1. create a new file (File → New Window)
2. type in: print("Hello world!")
3. run your program (Run → Run Module)
   • you will be prompted you to save your file
   • save your file as hello.py (make sure you keep the .py extension!)

Let's Take a Closer Look at "Hello World" …

print("Hello world!")

SPACE!

• notice there's no space prior to print
• Python is whitespace significant
  • whitespace matters
  • it mostly matters at the beginning of lines
  • indentation specifies the beginning and end of a group of lines of code
  • interior spacing usually doesn't matter
• this will work →

print  (      "Hello world!")

• this won't →

        print("Hello world!")

• we'll see more about spacing in our next class

Print

• print is a built-in function
• what's a function? →

Print Continued

• print is a built in function… that will output whatever you give it to the console followed by a new line
• you can tell it's a built-in function because it's highlighted (purple)
• if you start typing it and open parentheses, you get a hint →
  • notice - it can take more than one parameter or argument!
  • you can give print multiple parameters by separating them with a comma; all parameters will be printed out separated by a space →

print("Hi", "there")

A Quick Note About Functions

• we will go into the rest of the hint when we cover functions
• for now we're just interested in calling functions
• you call a function by
  • typing the function's name
  • open parentheses
  • any arguments (that is, values that you use as input for the function), separated by commas
  • close parentheses

a_function_name("argument 1", 2, 3.0)

A String

• the one argument that we pass to the print function is "Hello world!"
• this is called a string…
• it's just a sequence of characters
• note that it's surrounded by quotes!

One Last Look…

• a function named print
• being called with exactly one argument
• the one argument is a string:

print("Hello world!")

A Reminder About a Neat Trick

Again… as mentioned previously, you can use help(thing) in the interactive shell to show information about built-in functions and other Python features:

>>> help(print)

Some More New Stuff

• we'll talk a little more about strings and other types of values
• comments
• the operations that you can use on those types
• variables
• user input
• design, input, processing and output

Let's Move on to Values and Data Types