Jargon

Introduction

Computing is full of funny words, and of ordinary words used in funny ways. We’ve tried not to use too much jargon in these sheets, but we haven’t always succeeded. So this sheet tries to give brief descriptions of what some funny words mean. If you run across something you don’t understand, it’s worth taking a quick look at this sheet.

Some of this jargon is general programming jargon. Some is specific to Python.

Lots of these entries refer to other entries, so if you see a word in here that you don’t understand you should look it up!

The jargon

argument
An object passed into a function when you call it. It appears inside the function as a local variable.
association
A piece of information that says If you’re given X, give back Y . A dictionary is made up of associations.
body
The code inside a loop, or function, or other complicated thing. So a function body is what gets obeyed when you call a function, and a loop body is what gets obeyed each time around a loop.
call
To call a function is to use it. Calling a function is a bit like copying out its definition and doing that.
class
Classes are kinds of object. (In the real world, things like computer and human and book are classes.
character
A letter, digit or other symbol. A string is made up of a sequence of characters.
code
The stuff that programs are made of. A piece of code is a portion of a program.
comment
A piece of a program that doesn’t do anything, but is there for people to read. Usually the purpose of a comment is to explain what the code around it is doing.
condition
Something that might be true or false, like 1 > 2 or does x equal y?.
conditional
Something that depends on a condition, like an if statement.
definition
A bit of code that tells the computer what something is: what value a variable has, or what a function ought to do, or all about a class.
dictionary
A Python object a bit like a dictionary, an address book or an encyclopaedia. A dictionary is made up of associations.
element
An item in a sequence.
exception
An unusual situation in which something has gone wrong, or a Python object describing such a situation. A pretentious way of saying error.
expression
A calculation that produces a value. The simplest expressions are things like constants (123, 'eek') and variables (my_name). They can get much more complicated: 17 * a[a.index(func(99))] > 93 and a / (b + c) == 2.
for loop
A loop whose body gets obeyed once for each item in a sequence.
function
A set of instructions with a name. You can make the computer obey all the instructions by saying the name of the function.
global variable
A variable that exists everywhere in your program, not just inside one function.
graphics
Pictures drawn by a computer.
immutable
Not allowed to be changed.
import
To make the things inside a module available for use.
instance
An object described by a class. In the real world, computers and women and books are instances of the classes computer , human and book .
iteration
A single trip through a loop body. When the loop is obeyed, it will usually go through several iterations.
key
One half of an association in a dictionary: the half you can look things up by. If you say dict['zog']123, then the key is 'zog'.
list
An object made up of some number of other objects, in order. You can get at them by number.
local variable
A variable that exists only inside a particular function, not affecting anything outside the function.
loop
A piece of your program that might get obeyed over and over again.
module
A bunch of objects with names that you can import into your program.
object
Any piece of information Python can work with, like a number or string or list.
read
To get information into a program. For instance, if you ask the person sitting in front of the computer to type something in, that’s reading .
return
What a function does when it’s finished. If it returns a value , then the function call can be used in an expression.
sequence
A list or string or tuple. (Actually there are other kinds of sequence, but you don’t need to worry about those.
string
A sequence of characters, usually forming a piece of text.
subclass
A class, all of whose instances are also instances of another class. In the real world, Apple Macintosh is a subclass of computer , which is a subclass of electronic device , which is a subclass of thing.
tuple
A particular kind of sequence, written like this: (1, 2, 3). Unlike lists, tuples are immutable.
value
An object. The result of a calculation, or of a function call, or of referring to a variable. Also: one half of an association in a dictionary: the half you’re looking for when you do a lookup. If you say dict['zog']=123, then the value is 123.
variable
A name for an object. After saying x=6, x is a name for the object usually known as 6, and using x will usually do the same as using 6 would. x is called a variable because you can change what object it names.