Working in Python · Book Vocabulary ↪ AP CSP Vocabulary Coverage ↪ A-Z Glossary (merged)

Vocabulary by Chapter

Every term from Downey's own chapter-ending Glossary sections, chapters 1–18, plus any interludes' own glossaries, in reading order. This is the book's own vocabulary, exactly as written — not a paraphrase, not a standards crosswalk.

222

glossary terms, chapters 1–18 + 2 interludes

chapters with a Glossary section (plus 2 interludes)

on the AP CSP exam's own vocabulary list

^AP on the AP CSP exam's vocabulary list (Also ch. N.) also defined in another chapter — link jumps there

Chapter 1 — Welcome

17 terms

Term	Definition
arithmetic operator	A symbol, like `+` and `*`, that denotes an arithmetic operation like addition or multiplication.
integer^AP	A type that represents numbers with no fractional or decimal part.
floating-point	A type that represents integers and numbers with decimal parts.
integer division	An operator, `//`, that divides two numbers and rounds down to an integer.
expression^AP	A combination of variables, values, and operators.
value	An integer, floating-point number, or string — or one of other kinds of values we will see later. (Also ch. 10.)
function^AP	A named sequence of statements that performs some useful operation. Functions may or may not take arguments and may or may not produce a result.
function call	An expression — or part of an expression — that runs a function. It consists of the function name followed by an argument list in parentheses.
syntax error^AP	An error in a program that makes it impossible to parse — and therefore impossible to run.
string^AP	A type that represents sequences of characters.
concatenation^AP	Joining two strings end-to-end.
type^AP	A category of values. The types we have seen so far are integers (type `int`), floating-point numbers (type `float`), and strings (type `str`).
operand	One of the values on which an operator operates.
natural language	Any of the languages that people speak that evolved naturally.
formal language	Any of the languages that people have designed for specific purposes, such as representing mathematical ideas or computer programs. All programming languages are formal languages.
bug	An error in a program.
debugging^AP	The process of finding and correcting errors.

Chapter 2 — Variables and Statements

15 terms

Term	Definition
variable^AP	A name that refers to a value.
assignment statement^AP	A statement that assigns a value to a variable.
state diagram	A graphical representation of a set of variables and the values they refer to.
keyword	A special word used to specify the structure of a program.
import statement	A statement that reads a module file so we can use the variables and functions it contains.
module^AP	A file that contains Python code, including function definitions and sometimes other statements.
dot operator	The operator, `.`, used to access a function in another module by specifying the module name followed by a dot and the function name.
evaluate	Perform the operations in an expression in order to compute a value.
statement	One or more lines of code that represent a command or action.
execute	Run a statement and do what it says.
argument^AP	A value provided to a function when the function is called.
comment^AP	Text included in a program that provides information about the program but has no effect on its execution.
runtime error^AP	An error that causes a program to display an error message and exit.
exception	An error that is detected while the program is running.
semantic error^AP	An error that causes a program to do the wrong thing, but not to display an error message. (Also ch. 6b.)

Chapter 3 — Functions

10 terms

Term	Definition
function definition	A statement that creates a function.
header	The first line of a function definition.
body	The sequence of statements inside a function definition.
function object	A value created by a function definition. The name of the function is a variable that refers to a function object.
parameter^AP	A name used inside a function to refer to the value passed as an argument.
loop^AP	A statement that runs one or more statements, often repeatedly.
local variable	A variable defined inside a function, and which can only be accessed inside the function.
stack diagram	A graphical representation of a stack of functions, their variables, and the values they refer to.
frame	A box in a stack diagram that represents a function call. It contains the local variables and parameters of the function.
traceback	A list of the functions that are executing, printed when an exception occurs.

Chapter 4 — Functions and Interfaces

11 terms

Term	Definition
interface design^AP	A process for designing the interface of a function, which includes the parameters it should take.
canvas	A window used to display graphical elements including lines, circles, rectangles, and other shapes.
encapsulation	The process of transforming a sequence of statements into a function definition.
generalization	The process of replacing something unnecessarily specific (like a number) with something appropriately general (like a variable or parameter).
keyword argument	An argument that includes the name of the parameter.
refactoring	The process of modifying a working program to improve function interfaces and other qualities of the code.
development plan	A process for writing programs.
docstring^AP	A string that appears at the top of a function definition to document the function's interface. (Also ch. 6b.)
multiline string	A string enclosed in triple quotes that can span more than one line of a program.
precondition	A requirement that should be satisfied by the caller before a function starts.
postcondition	A requirement that should be satisfied by the function before it ends.

Chapter 5 — Conditionals and Recursion

15 terms

Term	Definition
recursion	The process of calling the function that is currently executing.
modulus operator^AP	An operator, `%`, that works on integers and returns the remainder when one number is divided by another.
boolean expression^AP	An expression whose value is either `True` or `False`.
relational operator^AP	One of the operators that compares its operands: `==`, `!=`, `>`, `<`, `>=`, and `<=`.
logical operator^AP	One of the operators that combines boolean expressions, including `and`, `or`, and `not`.
conditional statement^AP	A statement that controls the flow of execution depending on some condition. Informally, this is usually an `if`-statement (that might contain an elif and else).
condition	The boolean expression in a conditional statement that determines which branch runs.
block	One or more statements indented to indicate they are part of another statement. Statements in a block are frequently said to have the same scope.
branch	One of the alternative sequences of statements in a conditional statement.
chained conditional	A conditional statement with a series of alternative branches.
nested conditional^AP	A conditional statement that appears in one of the branches of another conditional statement.
recursive	A function that calls itself is recursive.
base case	A conditional branch in a recursive function that does not make a recursive call.
infinite recursion	A recursion that doesn't have a base case, or never reaches it. Eventually, an infinite recursion causes a runtime error.
newline	A character that creates a line break between two parts of a string.

Chapter 6 — Return Values

8 terms

Term	Definition
return value^AP	The result of a function. If a function call is used as an expression, the return value is the value of the expression.
side effect	Any effect a function has other than returning a value, such as displaying output or drawing on a canvas.
pure function	A function that returns a value and has no side effects. (Also ch. 14.)
dead code	Part of a program that can never run, often because it appears after a `return` statement.
incremental development^AP	A program development plan intended to avoid debugging by adding and testing only a small amount of code at a time.
scaffolding	Code that is used during program development but is not part of the final version.
Turing complete	A language, or subset of a language, is Turing complete if it can perform any computation that can be described by an algorithm.
input validation	Checking the parameters of a function to make sure they have the correct types and values

Interlude — Docstrings and Doctests

18 terms

Term	Definition
docstring^AP	A string at the beginning of a function that documents what the function does; unlike a comment, it is stored on the function and can be read by the program. (Python's name for what the exam calls program documentation.) (Also ch. 4.)
doctest	An example call and its expected result, written inside a docstring, that can be run automatically to check the function. (Python; not exam vocabulary.)
testing^AP	Checking that a program behaves correctly by running it on chosen inputs and comparing what comes out against what should have come out.
test case^AP	A single input, paired with the result it should produce.
boundary case	A test case at the value where a function's behavior changes, such as zero, an empty string, or the first or last item.
edge case	A test case at an unusual or extreme input, where a function is most likely to be wrong.
expected value	What a test says the answer should be, as opposed to what the code actually produced.
pass	A test whose actual result matches its expected value. (Also ch. 7.)
fail	A test whose actual result does not match its expected value. (Also ch. 7.)
hand tracing^AP	Working through code on paper line by line, writing down each variable's value, in order to find an error without running the program.
semantic error^AP	An error that lets the program run but produces a wrong result. (The exam calls this a logic error.) (Also ch. 2.)
roundoff error^AP	A loss of precision that happens because a fixed number of bits cannot represent some numbers exactly. (Also ch. 7b.)
program purpose^AP	The need a program serves, or the problem it solves; why it exists.
program function^AP	What a program does when it runs, described as behavior.
program input^AP	Data a program receives while it is running.
program output^AP	What a program produces: displayed text, a returned value, a file, a sound, a movement.
procedure^AP	The exam's word for a named, reusable block of code, whether or not it returns a value. This book says function. In older languages the two words were distinct: a procedure returned nothing, a function returned a value.
regression	A bug that reappears in code that used to work. Tests exist mainly to catch these. (Professional vocabulary, not exam vocabulary.)

Chapter 7 — Iteration and Search

11 terms

Term	Definition
loop variable	A variable defined in the header of a `for` loop.
file object	An object that represents an open file and keeps track of which parts of the file have been read or written.
method	A function that is associated with an object and called using the dot operator. (Also ch. 15.)
update	An assignment statement that give a new value to a variable that already exists, rather than creating a new variables.
initialize	Create a new variable and give it a value.
increment	Increase the value of a variable.
decrement	Decrease the value of a variable.
counter	A variable used to count something, usually initialized to zero and then incremented.
linear search^AP	A computational pattern that searches through a sequence of elements and stops when it finds what it is looking for.
pass	If a test runs and the result is as expected, the test passes. (Also ch. 6b.)
fail	If a test runs and the result is not as expected, the test fails. (Also ch. 6b.)

Interlude — Representing Data

18 terms

Term	Definition
bit^AP	A single binary digit, 0 or 1.
byte^AP	Eight bits. Enough to hold one of 256 values.
binary^AP	Base-2 representation, using only the digits 0 and 1.
decimal^AP	Base-10, the system you already use.
hexadecimal^AP	Base-16, using 0 through 9 and A through F. Four bits per digit, so one byte is exactly two hex digits.
digital data^AP	Values represented in discrete steps, ultimately as bits.
analog data^AP	Values that vary continuously and smoothly, with no steps.
sampling^AP	Approximating an analog signal by measuring it at regular intervals. Two independent settings: how often you measure (rate) and how precisely you record each measurement (bit depth).
ASCII^AP	A table assigning a number from 0 to 127 to each of a small set of characters.
Unicode^AP	A far larger table, covering the writing systems ASCII left out.
character encoding	The agreement about which numbers stand for which characters. Read bits with the wrong encoding and you get the right data as the wrong text.
RGB^AP	Color stored as three numbers, the amounts of red, green, and blue, each usually one byte.
overflow error^AP	An error that happens when a value is too large for the number of bits available to hold it.
roundoff error^AP	A loss of precision that happens because a fixed number of bits cannot represent some numbers exactly. (Second reference — first defined by the interlude between chapters 6 and 7.)
lossless compression^AP	Reduces size while allowing the original to be reconstructed exactly.
lossy compression^AP	Reduces size further, but only an approximation of the original can be recovered.
compression ratio	Compressed size divided by original size. (This book's own term; not exam vocabulary.)
run-length encoding	A lossless scheme that replaces runs of a repeated value with the value and a count. (This book's own term; the exam names no specific algorithm.)

Chapter 8 — Strings and Regular Expressions

12 terms

Term	Definition
sequence	An ordered collection of values where each value is identified by an integer index.
character	An element of a string, including letters, numbers, and symbols.
index^AP	An integer value used to select an item in a sequence, such as a character in a string. In Python indices start from `0`.
slice	A part of a string specified by a range of indices.
empty string	A string that contains no characters and has length `0`.
object	Something a variable can refer to. An object has a type and a value.
immutable	If the elements of an object cannot be changed, the object is immutable.
invocation	An expression — or part of an expression — that calls a method.
regular expression	A sequence of characters that defines a search pattern.
pattern	A rule that specifies the requirements a string has to meet to constitute a match.
string substitution	Replacement of a string, or part of a string, with another string.
shell command	A statement in a shell language, which is a language used to interact with an operating system.

Chapter 9 — Lists

9 terms

Term	Definition
list^AP	An object that contains a sequence of values.
element^AP	One of the values in a list or other sequence.
nested list	A list that is an element of another list.
delimiter	A character or string used to indicate where a string should be split.
equivalent	Having the same value.
identical	Being the same object (which implies equivalence).
reference	The association between a variable and its value.
aliased	If there is more than one variable that refers to an object, the object is aliased.
attribute	One of the named values associated with an object. (Also ch. 14.)

Chapter 10 — Dictionaries

12 terms

Term	Definition
dictionary	An object that contains key-value pairs, also called items.
item	In a dictionary, another name for a key-value pair.
key	An object that appears in a dictionary as the first part of a key-value pair.
value	An object that appears in a dictionary as the second part of a key-value pair. This is more specific than our previous use of the word "value". (Also ch. 1.)
mapping	A relationship in which each element of one set corresponds to an element of another set.
hash table	A collection of key-value pairs organized so that we can look up a key and find its value efficiently.
hashable	Immutable types like integers, floats and strings are hashable. Mutable types like lists and dictionaries are not.
hash function	A function that takes an object and computes an integer that is used to locate a key in a hash table. (Also ch. 13.)
accumulator	A variable used in a loop to add up or accumulate a result.
filtering^AP	Looping through a sequence and selecting or omitting elements.
call graph	A diagram that shows every frame created during the execution of a program, with an arrow from each caller to each callee.
memo	A computed value stored to avoid unnecessary future computation.

Chapter 11 — Tuples

6 terms

Term	Definition
pack	Collect multiple arguments into a tuple.
unpack	Treat a tuple (or other sequence) as multiple arguments.
zip object	The result of calling the built-in function `zip`, can be used to loop through a sequence of tuples.
enumerate object	The result of calling the built-in function `enumerate`, can be used to loop through a sequence of tuples.
sort key	A value, or function that computes a value, used to sort the elements of a collection.
data structure	A collection of values, organized to perform certain operations efficiently.

Chapter 12 — Text Analysis and Generation

8 terms

Term	Definition
default value	The value assigned to a parameter if no argument is provided.
override	To replace a default value with an argument.
deterministic	A deterministic program does the same thing each time it runs, given the same inputs.
pseudorandom^AP	A pseudorandom sequence of numbers appears to be random, but is generated by a deterministic program.
bigram	A sequence of two elements, often words.
trigram	A sequence of three elements.
n-gram	A sequence of an unspecified number of elements.
rubber duck debugging	A way of debugging by explaining a problem aloud to an inanimate object.

Chapter 13 — Files and Databases

16 terms

Term	Definition
ephemeral	An ephemeral program typically runs for a short time and, when it ends, its data are lost.
persistent	A persistent program runs indefinitely and keeps at least some of its data in permanent storage.
directory	A collection of files and other directories.
current working directory	The default directory used by a program unless another directory is specified.
path	A string that specifies a sequence of directories, often leading to a file.
relative path	A path that starts from the current working directory, or some other specified directory.
absolute path	A path that does not depend on the current directory.
f-string	A string that has the letter `f` before the opening quotation mark, and contains one or more expressions in curly braces.
configuration data	Data, often stored in a file, that specifies what a program should do and how.
serialization	Converting an object to a string.
deserialization	Converting a string to an object.
database	A file whose contents are organized to perform certain operations efficiently.
key-value stores	A database whose contents are organized like a dictionary with keys that correspond to values.
binary mode	A way of opening a file so the contents are interpreted as sequence of bytes rather than a sequence of characters.
hash function	A function that takes and object and computes an integer, which is sometimes called a digest. (Also ch. 10.)
digest	The result of a hash function, especially when it is used to check whether two objects are the same.

Chapter 14 — Classes and Functions

12 terms

Term	Definition
object-oriented programming	A style of programming that uses objects to organize code and data.
class	A programmer-defined type. A class definition creates a new class object.
class object	An object that represents a class — it is the result of a class definition.
instantiation	The process of creating an object that belongs to a class.
instance	An object that belongs to a class.
attribute	A variable associated with an object, also called an instance variable. (Also ch. 9.)
object diagram	A graphical representation of an object, its attributes, and their values.
format specifier	In an f-string, a format specifier determines how a value is converted to a string.
pure function	A function that does not modify its parameters or have any effect other than returning a value. (Also ch. 6.)
functional programming style	A way of programming that uses pure functions whenever possible.
prototype and patch	A way of developing programs by starting with a rough draft and gradually adding features and fixing bugs.
design-first development	A way of developing programs with more careful planning that prototype and patch.

Chapter 15 — Classes and Methods

8 terms

Term	Definition
object-oriented language	A language that provides features to support object-oriented programming, notably user-defined types.
method	A function that is defined inside a class definition and is invoked on instances of that class. (Also ch. 7.)
receiver	The object a method is invoked on.
static method	A method that can be invoked without an object as receiver.
instance method	A method that must be invoked with an object as receiver.
special method	A method that changes the way operators and some functions work with an object.
operator overloading	The process of using special methods to change the way operators with with user-defined types.
invariant	A condition that should always be true during the execution of a program.

Chapter 16 — Classes and Objects

3 terms

Term	Definition
shallow copy	A copy operation that does not copy nested objects.
deep copy	A copy operation that also copies nested objects.
polymorphism	The ability of a method or operator to work with multiple types of objects.

Chapter 17 — Inheritance

8 terms

Term	Definition
inheritance	The ability to define a new class that is a modified version of a previously defined class.
encode	To represent one set of values using another set of values by constructing a mapping between them.
class variable	A variable defined inside a class definition, but not inside any method.
totally ordered	A set of objects is totally ordered if we can compare any two elements and the results are consistent.
delegation	When one method passes responsibility to another method to do most or all of the work.
parent class	A class that is inherited from.
child class	A class that inherits from another class.
specialization	A way of using inheritance to create a new class that is a specialized version of an existing class.

Chapter 18 — Python Extras

5 terms

Term	Definition
factory	A function used to create objects, often passed as a parameter to a function.
conditional expression	An expression that uses a conditional to select one of two values.
list comprehension	A concise way to loop through a sequence and create a list.
generator expression	Similar to a list comprehension except that it does not create a list.
test discovery	A process used to find and run tests.

Full definitions and provenance in the repo-local twin of this page. Cross-links: the alignment/glossary-map.md (concept-level crosswalk, Pass 3, repo-only), the AP CSP Coverage Map (topic-level), and the AP CSP Standards Reference.