Glossary

---

argument

A value given to a function or program when it runs. The term is often used interchangeably (and inconsistently) with parameter.

assign

To give a value a name by associating a variable with it.

body

(of a function): the statements that are executed when a function runs.

case-insensitive

Treating text as if upper and lower case characters of the same letter were the same. See also: case-sensitive.

case-sensitive

Treating text as if upper and lower case characters of the same letter are different. See also: case-insensitive.

comment

A remark in a program that is intended to help human readers understand what is going on, but is ignored by the computer. Comments in Python, R, and the Unix shell start with a # character and run to the end of the line; comments in SQL start with --, and other languages have other conventions.

compose

To apply one function to the result of another, such as f(g(x)).

comma-separated values

(CSV) A common textual representation for tables in which the values in each row are separated by commas.

default value

A value to use for a parameter if nothing is specified explicitly.

delimiter

A character or characters used to separate individual values, such as the commas between columns in a CSV file.

documentation

Human-language text written to explain what software does, how it works, or how to use it.

dotted notation

A two-part notation used in many programming languages in which thing.component refers to the component belonging to thing.

empty string

A character string containing no characters, often thought of as the “zero” of text.

encapsulation

The practice of hiding something’s implementation details so that the rest of a program can worry about what it does rather than how it does it.

floating-point number

A number containing a fractional part and an exponent. See also: integer.

function

A named group of instructions that is executed when the function’s name is used in the code. Occurrence of a function name in the code is a function call. Functions may process input arguments and return the result back. Functions may also be used for logically grouping together pieces of code. In such cases, they don’t need to return any meaningful value and return a special value None, which is a way of saying “nothing” in Python.

function call

A use of a function in another piece of software.

global variable

A variable defined outside of a function. It can be used in global statements, and read inside functions.

import

To load a library into a program.

in-place operators

An operator such as += that provides a shorthand notation for the common case in which the variable being assigned to is also an operand on the right hand side of the assignment. For example, the statement x += 3 means the same thing as x = x + 3.

index

A subscript that specifies the location of a single value in a collection, such as a single pixel in an image.

integer

A whole number, such as -12343. See also: floating-point number.

library

A family of code units (functions, classes, variables) that implement a set of related tasks.

local variable

A variable defined inside of a function, that exists only in the scope of that function, meaning it cannot be accessed by code outside of the function.

member

A variable contained within an object.

method

A function which is tied to a particular object. Each of an object’s methods typically implements one of the things it can do, or one of the questions it can answer.

notebook

Interactive computational environment accessed via your web browser, in which you can write and execute Python code and combine it with explanatory text, mathematics and visualizations. Examples are IPython or Jupyter notebooks.

object

A collection of conceptually related variables (members) and functions using those variables (methods).

parameter

A variable named in the function’s declaration that is used to hold a value passed into the call. The term is often used interchangeably (and inconsistently) with argument.

regression

To re-introduce a bug that was once fixed.

sequence

A collection of information that is presented in a specific order. For example, in Python, a string is a sequence of characters, while a list is a sequence of any variable.

shape

An array’s dimensions, represented as a vector. For example, a 5×3 array’s shape is (5,3).

silent failure

Failing without producing any warning messages. Silent failures are hard to detect and debug.

slice

A regular subsequence of a larger sequence, such as the first five elements or every second element.

string

Short for “character string”, a sequence of zero or more characters.

syntax

The rules that define how code must be written for a computer to understand.

syntax error

A programming error that occurs when statements are in an order or contain characters not expected by the programming language.

tab completion

A feature of command-line interpreters, in which the program automatically fills in partially typed commands upon pressing the Tab key.

type

The classification of something in a program (for example, the contents of a variable) as a kind of number (e.g. floating-point, integer), string, or something else.

type of error

Indicates the nature of an error in a program. For example, in Python, an IOError to problems with file input/output. See also: syntax error.

variable

A value that has a name associated with it.