5.1: Background

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Virtually all modern programming languages make us of an IDE, or Integrated Development Environment, which allows the creation, editing, testing, and saving of programs and modules. In Python, the IDE is called IDLE (like many items in the language, this is a reference to the British comedy group Monty Python, and in this case, one of its members, Eric Idle).

Before opening IDLE, it is worth recalling that there are three basic types of simple variables in Python: integers (whole numbers, commonly used as an index), floats (that is, numbers with a decimal point, AKA real numbers), and strings (collections of alphanumeric characters such as names, sentences, or numbers that are not manipulated mathematically such as a part number or zip code). A legal variable name must start with a letter. It is then optionally followed by some collection of letters, numerals and the underscore. It cannot contain any other characters or spaces, and cannot be a reserved word (i.e., a word with a special meaning in the language such as a command or operator). In Python, variables may be created by simply declaring them and assigning a value to them. Examples include:

a=2.3
name=”Joe”

It is best to think of the equal sign as “gets”. That is, think of the first example as “the variable a gets the floating point value 2.3” and the second as “the variable name gets the string Joe”. An assignment command such as these literally reserves space in the computer’s memory for the variable and tags it with the variable name. Then, it stores the appropriate value at that location for future use.