python_learners_glossary

Definitions of Python jargon to help Python beginners understand Pythonista gobbletigook. The idea is to help a Python beginner's understanding even before they've learned to write the code.

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Clarity
Conciseness
Accuracy

... are all desirable - in that order. Don't get pedantic or hung up on corner cases_.

Terms to define are not strictly Python terms, but any terms likely to be frequently heard at a Python conference.

To reduce cognitive load, let's use examples around a consistent, familiar theme: cats.

Glossary

General

.. class:: basic general .. _execute:

Execute Go. Run. Do that thing you do. Nothing to do with beheading anybody.

.. _code:

Code Collection of computer instructions in a human-readable computer/programming language.

.. _comment: .. _comments:

Comment To clarify something in the middle of a piece of code_. If used properly can make understanding your code_ much easier than if they weren't present.

Numeral systems

.. _decimal:

Decimal A numeral system of base 10, which means it has 10 digits to represent numbers. As long as you only have ten digits, your system can be called decimal, but it is conventional to use from 0 to 9.

It is the standard today.

Example: 20 octal_ is 16 decimal_

.. _binary:

Binary A numeral system of base 2, which means it has 2 digits to represent numbers. As long as you only have two digits, your system can be called binary, but it is conventional to use 0 and 1.

Example: 12 octal_ is 1010 binary_

.. _octal:

Octal A numeral system of base 8, which means it has 8 digits to represent numbers. As long as you only have eight digits, your system can be called octal, but it is conventional to use from 0 to 7.

Example: 80 decimal_ is 120 octal_

.. _hexadecimal: .. _hex:

Hexadecimal (or Hex) A numeral system of base 16, which means it has 16 digits to represent numbers. As long as you only have sixteen digits, your system can be called hexadecimal, but it is conventional to use from 0 to 9 and A to F.

Example: 123 decimal_ is 7B hex_

Data

.. class:: basic data .. _value:

Value A single piece of data, like 3 or 'Fluffy'

.. class:: basic data .. _literal:

Literal A representation of a value as the value itself, as opposed to the result of a function_ or expression_.

"Whiskers"  # a string literal
'Whiskers'  # a string literal
1  # an integer literal
1.5  # a float literal
["Whiskers", 10]  # a list literal

.. class:: basic data

String A piece of text data, like 'hello'. Enclosing it in quotation marks tells Python that it's a string and not something like a variable_ name.

.. class:: basic data

Float Short for floating-point number, a number with a decimal point.

.. class:: basic data

.. _variable:

Variable A piece of data that has a name.

  cat_name = 'Fluffy'

Now cat_name is a variable with the value_ 'Fluffy'.

.. class:: basic data

Assign Give a name to a value_, making a variable_.

.. class:: basic data .. _expression:

Expression A description of a value that contains calculations and/or other executable code; the code must be executed to determine the expression's actual value. Typically, these fit on one line, but not necessarily.

Examples::

  'lazy ' + 'cat'  # Evaluates to 'lazy cat'
  2 * 2 > 100  # Evaluates to ``False``

.. class:: basic data

Boolean True or False.

.. class:: basic data .. _list:

List A series of values. Python will remember what order they come in.

  ['Mouser', 17, 'Whiskers']

.. class:: basic data

Tuple A series of values. Python will remember what order they come in.

Hey, is that the same as a list_? It's very similar, but after a tuple is set up, you're not allowed to change it.

  ('Mouser', 17, 'Whiskers')

.. class:: basic data

Set Just like in mathematics - a group of values. Python will not necessarily remember what order they came in, and each value_ can only appear in the set once.

Functions

.. class:: basic functions .. _function:

Function A named series of instructions. Its definition begins with the def keyword.

  def feed_cat(kg_of_food, kg_of_cat):
      kg_of_food = kg_of_food - 0.1
      kg_of_cat = kg_of_cat + 0.1

.. class:: basic functions .. _call: .. _called:

Call Tell a function_ to execute_. To call a function, give its name followed by parenthesis containing its arguments_ (if any).

  feed_cat(8.0, 3.0)

.. class:: basic functions .. _argument: .. _arguments:

Argument A piece of data that you "pass" (give) to a function_ as you call_ it. In our feed_cat function_, kg_of_food and kg_of_cat are the function's arguments.

.. class:: basic functions

Parameter Synonym for argument_.

Return Stop running a function_ and return to the place where the function was called_ from. Send a value_ back - the "return value".

Object-oriented

.. class:: basic object-oriented .. _object: .. _objects:

Object A logical grouping of functions (called "methods_" in this context) and variables (called "attributes_" in this context).

.. class:: basic object-oriented .. _method: .. _methods:

Method A function that belongs to an object and "knows" about the object it belongs to. For instance, if my_cat is an object that has a speak method, then we can call_ it::

  my_cat.speak()
  'meow'

... and my_cat.speak doesn't need to be told what kind of animal should speak, because it already knows that it belongs to my_cat.

.. class:: basic object-oriented .. attribute_: .. attributes_:

Attribute A piece of data that belongs to an object. This object, my_cat, has a name attribute with the value 'Agamemnon'.``

  my_cat.name
  'Agamemnon'

.. class:: basic object-oriented .. _class: .. _classes:

Class A code template, used for creating and initializing an object_ with pre-defined data, and for providing code to operate on that object's data.

.. class:: basic object-oriented

Instance An object_ of a given class_. my_cat is an instance of the class Cat.

.. class:: intermediate object-oriented

Instantiate Create a new instance of a given class. When my_cat has kittens, she is instantiating several new instances of the class Cat. (Please spay our neuter your pets!)

.. class:: basic object-oriented

Object-oriented programming_ Programming that makes use of classes_ and objects_.

.. class:: intermediate object-oriented

Dunder The two underscores before and after a method name to indicate that it is "magic", i.e. init, new, etc. (Short for "Double-underscore")

.. class:: intermediate object-oriented

Magic Method Methods that can be used to change the normal behavior of an object. HINT : in Python, everything is an object.

Program Structure

.. class:: basic program_structure .. _module:

Module_ A single file of Python commands. Calling it a module implies we plan to "import" it, not just call it on its own.

.. class:: basic program_structure .. _package:

Package_ A directory full of modules that can all together be referred to by the package's name.

.. class:: basic program_structure

Import Make the contents of a module_ or package_ available in your current program, even though it comes outside your current program's file.

Tools

.. class:: basic tools .. _editor:

Editor A program to create or change files. We usually mean text editor, since a Python program is a kind of text file. Notepad is an example of an editor (but don't use Notepad to edit Python, it can introduce mistakes into your Python programs; Notepad++_ is a good alternative).

.. _Notepad++: https://notepad-plus-plus.org/

.. class:: basic tools

IDE_ Abbreviation for Integrated Development Environment. A kind of text editor_ with programming-related superpowers; a program that lets you build more programs. Examples include Eclipse, Sublime, Wingware, and IDLE

.. class:: basic tools

Database_ A place to store data outside the program, possibly in memory ("in-memory databases") but generally on disk. A file on disk could be considered a very simple database, but we usually mean much more advanced programs.

.. class:: intermediate tools

.. _relational database:

Relational database A very common kind of database that's good at retrieving data that have relationships to one another. For instance, a question like "How expensive is the cat food brand that most of my cats prefer?" is usually easier to answer in a relational database than in other types of database.

.. class:: intermediate tools

RDBMS Relational database management system - basically a synonym for relational database.

.. class:: basic tools

SQL The specialized language usually used to get and manipulate data in a relational database_.

.. class:: intermediate tools

SQL database More or less a synonym for relational database_.

.. class:: intermediate tools

.. _non-relational database: An alternative to a relational database. It's generally easier to use and often faster to run, but has its own disadvantages for complex kinds of data access.

.. class:: intermediate tools

.. NoSQL database: More or less a synonym for non_relational database_.

.. class:: intermediate tools

REPL An interactive programming language interpreter that allows a user to type in statements which are immediately evaluated. The term REPL is an acronym for Read-Evaluate-Print-Loop.

Techniques

.. class:: basic techniques

.. _bug: .. _bugs:

Bug A mistake in software that makes it crash or behave badly.

.. class:: basic techniques

Debug Find and fix bugs_ in code_

.. class:: basic techniques

Refactor Change a program so that the functionality seems the same from the user's point of view, but the code itself is better - easier to read, understand, maintain, etc.

.. class:: basic techniques

Agile Development A systematic approach to software development that emphasizes short, concentrated periods of work on specific features or enhancements, where such features are delivered independently of the project at large

Contrast with the Waterfall Model_.

.. _Waterfall model: https://en.wikipedia.org/wiki/Waterfall_model