Built-ins

print

Prints the value to the screen.

print(5) prints the number 5 to the screen.

addition

Adds two numbers.

2 + 3 has the value 5.

subtraction

Subtracts the first number by the second.

3 - 1 has the value 2.

multiplication

Multiplies two numbers.

4 * 3 has the value 12.

division

Divides the first number by the second.

12 / 3 has the value 4.0 since division always results in a floating point number.

unary plus

Used on one value, does not change the number.

+ 3 has the value 3.

negation

Used on one value, negates the number.

- 3 has the value -3.

quotient

Calculates the quotient when the first number is divided by the second.

20 // 7 has the value 2, since the integer part of 20 divided by 7 is 2.

remainder

Calculates the remainder when the first number is divided by the second.

20 % 7 has the value 6, since the remainder when dividing 20 by 7 is 6.

exponentiation

Raises the first number to the power of the second number.

2 ** 3 has the value 8, since it is the cube of 2.

import

Used to import a module.

import math can be used to import the math module.

math module

The math module. Contains functions and constants relating to math.

After the math module is imported, math.sqrt and other functions and constants can be used.

square root

Determines the square root of the input. In the math module.

After the math module is imported, math.sqrt(4) has the value 2.0, since taking the square root always results in a floating point number.

pi

The constant (\pi). In the math module.

After the math module is imported, the constant can be accessed as math.pi.

directory

Used with the input __builtins__ (to list all built-ins), a value (to list all built-ins applicable to that value), or a module (to list all contents of the module).

Using dir(9) results in all functions that can be used on 9.

import a single function or constant

Used to import a single function or constant from a module.

After using from math import sqrt one can use sqrt instead of math.sqrt.

exponentiation

Uses the first input as the base and the second as the exponent. There are two versions. The version in the math module always returns a floating point number.

pow(2, 3) has the value 8 and math.pow(2, 3) has the value 8.0.

absolute value

Produces the absolute value of the input.

abs(-3.4) has the value 3.4.

documentation

Prints the docstring. Uses dot notation.

The docstring for abs has the lines abs(number) -> number and Return the absolute value of the argument..

user input

Prompts the user to type a value. The optional string is the prompt.

The function call input("Enter your age:") prompts the user for input with "Enter your age:".

determine type

Produces the type of the input.

The value of type(5) is <class 'int'>, indicating that 5 is an integer.

make into integer

Makes an integer, floating point number, or string (if an integer in quotation marks) into an integer.

The values of int(5.3) and int("5") are both 5.

make into floating point

Makes an integer, floating point number, or string (if a number in quotation marks) into a floating point number.

The values of float(5) and float("5") are both 5.0.

make into string

Makes a number or a string into a string.

The values of str(5) and str(5.0) are the strings "5", and "5.0", respectively.

length

Produces the length of a string.

The values of length("") and length("cat") are 0 and 3, respectively.

index

Produces the character in position i of a string.

The value of "cat"[1] is "a", since the first position is at index zero.

concatenation

Produces the string formed by gluing together the input strings.

The value of "hot" + "dog" is the string "hotdog".

repeated concatenation

Produces the string formed by repeatedly gluing the input with copies of the input.

The value of 2 * "no" is "nono".

slice

Produces a substring from positions a up to but not including position b.

The value of "hotdog"[2:5] is "tdo".

upper case

Produces a string with all lower-case letters replaced by upper-case letters. Uses dot notation.

The value of "Ha!".upper() is "HA!".

lower case

Produces a string with all upper-case letters replaced by lower-case letters. Uses dot notation.

The value of "Ha!".lower() is "ha!".

ceiling

Produces the integer reached by pushing up to the ceiling. In the math module.

The values of math.ceil(2), math.ceil(1.2), and math.ceil(-1.2) are 2, 2, and -1, respectively.

floor

Produces the integer reached by pushing down to the floor. In the math module.

The values of math.floor(2), math.floor(1.2), and math.floor(-1.2) are 2, 1, and -2, respectively.

truncation

Produces the integer formed by cutting off all digits after the decimal point. In the math module.

The values of math.trunc(2), math.trunc(1.2), and math.trunc(-1.2) are 2, 1, and -1, respectively.

true

The Boolean constant True.

If the value of a Boolean is not True, it must be False.

false

The Boolean contant False.

If the value of a Boolean is not False, it must be True.

or

Produces True when at least one smaller expression is True.

The value of True or False is True.

and

Produces True when both smaller expressions are True.

The value of True and True is True.

not

Produces True when the value is False and False when the value is True.

The value of not True is False.

less than

Produces True when the first input has a value less than the second input.

The value of 3 < 2 is False.

greater than

Produces True when the first input has a value greater than the second input.

The value of 5 > 2 is True.

less than or equal to

Produces True when the first input has a value less than or equal to the second input.

The value of 3 <= 3 is True.

greater than or equal to

Produces True when the first input has a value greater than or equal to the second input.

The value of 5 >= 10 is False.

equals

Produces True when the first input has a value equal to the second input.

The value of 1 == 0 is False.

not equals

Produces True when the first input has a value not equal to the second input.

The value of 2 != 2 is False.

is

Produces True when the first and second input are at the same memory address. Syntax is a is b.

For a variable num, the value of num is num is True.

is not

Produces True when the first and second input are not at the same memory address. Syntax is a is not b.

The value of a is not b is True whenever a is b is False.

code point from character

Produces the code point corresponding to the input character.

The value of ord("A") is 65.

character from code point

Produces the character corresponding to the input code point.

The value of chr(65) is "A".

letter check

Produces True if the input string is made up of letters. Uses dot notation.

The value of "Cat".isalpha() is True.

lower case check

Produces True if the input string is made up of lower-case letters. Uses dot notation.

The value of "cat".islower() is True.

upper case check

Produces True if the input string is made up of upper-case letters. Uses dot notation.

The value of "CAT".isupper() is True.

digit check

Produces True if the input string is made up of digits. Uses dot notation.

The value of "123".isdigit() is True.

space check

Produces True if the input string is made up of blank spaces. Uses dot notation.

The value of " ".isspace() is True.

assertion

Results in an assertion error if the Boolean expression after assert is not True.

Running a program containing the line assert 1 == 0, "No way" results in an assertion error with the message "No way".

list length

Produces the length of a list.

The value of len([1, 2, 3]) is 3, since the number of items in the list is 3.

index

Produces the item in position i of a list.

The value of [1, 2, 3][1] is 2, since 2 is the item in position 1 of the list.

concatenation

Produces the list formed by gluing together the input lists.

The value of [0, 1] + [2, 3] is the list [0, 1, 2, 3].

repeated concatenation

Produces the list formed by repeatedly gluing the input with copies of the input.

The value of [3, 4] * 2 is [3, 4, 3, 4], as it is formed by concatenating two copies of [3, 4].

slice

Produces a list from positions a up to but not including position b.

The value of [6, 7, 8, 9][1:3] is [7, 8], as it is formed of the items in positions 1 through 2.

minimum

Produces the minimum item in the list. The input list does not change.

The value of min([4, 3, 6]) is 3.

maximum

Produces the maximum item in the list. The input list does not change.

The value of max([4, 3, 6]) is 6.

count

Produces the number of times the input item appears in the input list. Uses dot notation. The input list does not change.

The value of [8, 7, 8, 9].count(8) is 2, since the value 8 appears two times in the list.

search

Produces the smallest index of a position containing the input item in the input list. Uses dot notation. The input list does not change.

The value of [8, 9, 7].index(9) is 1, since 9 is in position 1.

membership

Produces True if the item is in the list. Syntax is a in b.

The value of 9 in [8, 9, 7] is True.

new list

Produces a new list containing the items of the input as items. The input list does not change.

The value of list("ape") is ["a", "p", "e"].

sorted

Produces a new list with the input items in sorted order. The input list does not change.

The value of sorted([6, 3, 5]) is [3, 5, 6].

append

Mutates the input list by appending the input item to the end of the list.

For a variable seq with value [1, 2], using seq.append(3) results in seq becoming the list [1, 2, 3].

remove

Mutates the input list by removing the first occurrence of the input item from the list.

For a variable seq with value [7, 8, 7], using seq.remove(7) results in seq becoming the list [8, 7].

insert

Mutates the input list by inserting at the input index the input item.

For a variable seq with value [7, 8, 7], using seq.insert(2, 9) results in seq becoming the list [7, 8, 9, 7].

sort

Mutates the input list by sorting the items.

For a variable seq with value [4, 2, 3], using seq.sort() results in seq becoming the list [2, 3, 4].

range

Produces an immutable sequence of integers starting at start and stopping before stop at intervals of step. Input order is (start, stop, step). If step is missing, its default value is 1. If both step and start are missing, their default values are 1 and 0, respectively.

The value of range(3, 9, 2) is a structure with the values 3, 5, and 7.

split

Produces a list of strings from an input string. Uses dot notation.

The value of "a b c".split() is ['a', 'b', 'c'].

class definition

Creates a new class.

To create a class Oyster, the first line should be class Oyster: and the second line, indented, should have the docstring.

instance check

Produces True if the first input (an object) is a member of the second input (a class).

The value of isinstance(eye, Circle) is True if we have created an object eye of type Circle.

attribute check

Produces True if the first input (an object) has an attribute with the second input (a string) as its name.

The value of hasattr(eye, "colour") is True if the object eye is of a type with attribute colour.

directory

Used with an class name as input to show contents of a class.

Using dir(Circle) shows contents of the class Circle.

copy module

Contains functions related to copying.

To load the copy module, use import copy.

copy function

Makes a shallow copy. In the copy module.

To create a copy of an object eye, use copy.copy(eye). If the object contains other objects, those objects will not be copied.

deep copy function

Makes a deep copy. In the copy module.

To create a copy of an object eye in which all objects within it are also copied, use copy.deepcopy(eye).

tuple length

Produces the length of a tuple.

The value of len((1, 2, 3)) is 3, since the number of items in the tuple is 3.

index

Produces the item in position i of a tuple.

The value of (1, 2, 3)[1] is 2, since 2 is the item in position 1 of the tuple.

concatenation

Produces the tuple formed by gluing together the input tuples.

The value of (0, 1) + (2, 3) is the tuple (0, 1, 2, 3).

repeated concatenation

Produces the tuple formed by repeatedly gluing the input with copies of the input.

The value of (3, 4) * 2 is (3, 4, 3, 4), as it is formed by concatenating two copies of (3, 4).

slice

Produces a tuple from positions a up to but not including position b.

The value of (6, 7, 8, 9)[1:3] is (7, 8), formed of the items in positions 1 through 2.

tuple

Produces a tuple from the items in the input.

The value of tuple([1, 2]) is (1, 2).

minimum

Produces the minimum item in the tuple.

The value of min((4, 3, 6)) is 3.

maximum

Produces the maximum item in the tuple.

The value of max((4, 3, 6)) is 6.

count

Produces the number of times the input item appears in the input tuple. Uses dot notation.

The value of (8, 7, 8, 9).count(8) is 2, since the value 8 appears two times in the tuple.

search

Produces the smallest index of a position containing the input item in the input tuple. Uses dot notation.

The value of (8, 9, 7).index(9) is 1, since 9 is in position 1.

membership

Produces True if the item is in the tuple. Syntax is a in b.

The value of 9 in (8, 9, 7) is True.

new list

Produces a new list containing the items of the input tupleas items.

The value of list(("a", "p", "e)) is ["a", "p", "e"].

sorted

Produces a new list with the tuple input items in sorted order.

The value of sorted((6, 3, 5)) is [3, 5, 6].

access dictionary item

Produces the value associated with key i.

For a variable data assigned the value {'one': 'un', 'two': 'deux'}, the value of data['two'] is deux.

keys

Produces a list of keys in the dictionary. Uses dot notation.

For a variable data assigned the value {'one': 'un', 'two': 'deux'}, using data.keys() results in the keys one and two.

key, item pairs

Produces a list of key, item pairs. Uses dot notation.

For a variable data assigned the value {'one': 'un', 'two': 'deux'}, using data.items() results in the pairs ('one', 'un') and ('two', 'deux').

in

Produces True if the first input is a key in the second input (a dictionary). Syntax is a in b.

For a variable data assigned the value {'one': 'un', 'two': 'deux'}, the value of 'two' in data is True.

not in

Produces True if the first input is not a key in the second input (a dictionary). Syntax is a not in b.

For a variable data assigned the value {'one': 'un', 'two': 'deux'}, the value of 'three' not in data is True.

zip

Produces pairs of values from two input sequences.

Using zip('ha','ho') results in the pairs ('h', 'h') and ('a', 'o').