CQS Final

Where code is entered

code cell

constant

fixed values, those which dont change ex. string, numeric

print()

displays data as the output

strings

sequence of characters

letters, words, numbers

anything encased in single or double quotes

numeric constants

doesnt need quotes

only numbers

comments and how they help

anything following a #, doesnt return an output

improve readability, usually explain code, best practice to use them

line spaces…

do not impact the code!

value

basic unit of a program a letter, number, or other

types of values

integer, str, float, bool, dict, tuple, list

dont type integers with ___

commas

float

numbers with a decimal point, even if its .00

bool

boolean, true or false

type()

returns the type of a value - int,str, float, bool, list, dict, tuple

returned as <class ‘type’>

float()

changes an integer/string to a float

only strings that work with floats are numbers

adding different types of values

int/float + string = ERROR
int + int = INT
float + float = FLOAT

int + float = FLOAT

variables

a named place that stores a value and can retrieve it later. variable can change

assignment statement

creates new variables and gives them values

only one =

ex. x = 2

type of a variable is….

the type it is assigned to

rules of variables name

• cant start with a number (but can INCLUDE numbers)

• cant contain special characters (@,!, a space)

• cannot contain keyword/reserved words (False, class, continue, and)

• are case sensitive! (age and AGE are different)

statement

unit of code that the python interpreter can execute

operators

special symbols that represent computations

list of operators and functions

/ = divides, always makes a float

+adds

-subtracts

*multiplies

//will divide then truncate float to an integer (floored division)

% yields remainder when first number divided by the second (modulus operator)

** exponent

multiple operators follow….

PEMDAS/operator precedence

string concatenation

joining strings by linking them end to end

use a + or can use *

operands

values operators applied to

expressions

combination of values, variables, and operators

(value all by itself is considered an expression)

input()

gets a value for a variables from the user

can pass prompt before entering with a string in ()

what the user enters is always a string

\n

represents newline, special character that represents a line break

comparison operators. list and meaning

compares two operand and returns either True or False

== equal?

!= not equal

> greater than

< less than

>= greater than or equal to

<= less than or equal to

“is”

“is not”

logical operators, list and function

and

• only returns True if both statements are true

or

• only returns true if either statement is true

not

• negates boolean expression result

conditional execution

gives ability to check conditions and change behavior of program accordingly

ex. if (boolean):

function

boolean after an if statement known as ..

the condition

indentation portion after an if statement, else, try, etc.

the block, runs all statements in the block

if statements, try, etc are known as

compound statements, consist of more then one line

alternative execution

if (boolean):

function

else:

function

one alternative always executed, else never has conditional with it

alternatives known as branches

chain conditional

when more than 2 alternatives

if (boolean):

function

elif():

function

…..

else:

can have an infinite number of elifs

dont need an else statement, but if so should be at the end

nested conditions

when there is one condition within another

exception handling structure

used when we expect there to be an error in the program

Try:

any one which could create an error

Except:

what to do if there is an error

if try works, exception is skipped

two types of loops

indefinite and definite

indefinite loop

a while loop

indefinite # of iterations, until condition becomes False

iteration variable that changes each time with the loop

iteration

everytime we execute the body and come back to the beginning

iteration variable

the variable that changes with each time the loop executes and controls when it finishes

variable after for in the for loop is an example of an iteration variable

while loop set up and flow of execution

while (boolean):

function

1. evaluate condition,yield true or false

2. if false, exit while statement and continue at next statement

3. if true, execute body and go back to step one

no iteration variable results in…

an infinate loop

break statement

forces the end of a loop

usually comes in an if statement as part of a while loop

continue statement

skips the rest of the body and begins the next iteration

definite loops

ends after a set known period of iterations. # of iterations = items in the set

for iteration variable in sequence:

function

iteration variable moves through all set values in the sequence

function

a named sequence of statements

format of a function

function()

that in () is the argument

return of a function is the return value

two types of functions

built in and those we define ourselves

built in function

those provided as part of python

ex. type(), float(), int()

treated as reserved words

max()

gives max number in a sequence

in a string, this is the letter with the highest value (a is low value and uppercase less than lower)

min

gives min number in a sequence

or in a string, letter with the lowest value (a is low value)

len()

returns the number of items in an argument

for a string, this would be the number of characters

for a list and tuple, number of values

for dict, number of key - value pairs

making your own function

def funtionname()

defines, but gives no output

calling a function

using a function outside where it was defined

parameter

the variable we use in the function definition. handle that lets the code in function access arguments passed to the function when it is called

return statement

gives the value of the function back to where it was called, if we call a function but dont a return a value - we will just get “none”

fruitful function

produces a result or return value

void function

no result, or return keyword

slice

a segment of a sequence

how to get one letter from a string

string/variable[index]

how does an index match to a string

index 0 = first letter of the string

how to get a segment of a string and rules

string/variable[index:index]

returns the left index but not the right

if second number beyond end, stops at the end

how to segment from beginning of string

string/variable[:index]

how to segment to end of string

string/variable[index:]

methods

functions built into the object itself and available to any instance of the object

string methods….

can only be used with strings

dir()

returns directory of all the methods which can be used with the object and the properties of the object

string.upper()

puts all in uppercase

string.lower()

puts all in lowercase

string.find(term)

checks to see if a term exists in an existing string

if found, returns the index of the firs occurrence of the string

if not found, returns -1

word.strip()

gets rid of all spaces on the left AND right

word.lstrip()

gets rid of all spaces on the left

word.rstrip()

 gets rid of all spaces on the right

string.replace(term to find, term to replace with)

find the term and puts in substitute

replaces all occurrences of the string

no error if it cant be found

list

a sequence of values

can include: dicts, tuples, integers, floats, strings, or other lists. all data types!

stored in a variable

values in a list

elements or items

separated by a coma

a list must be enclosed in

[]

2nd way to create a list

list()

way to access parts of a list

listname[index]

mutable types

lists and dictionaries

how to change a list

listname[index] = replacement value

list concaatenation

use +

prints the values from the first list, then the seconf

slicing a list from beginning

list_name[:index]

slicing a list

list_name[index:index]

slicing a list to the end

list_name[index:]

how to add items to end of list

list_name.append(term)

adds to list in order added

can repeat term

ONLY ADDS TO END, CANNOT PASS INDEX

can only append one item at a ti

how to sort a list

list_name.sort()

organizes numbers from low to high

if strings, goes in alphabetical order

how to sort a list in reverse

list_name.sort(reverse=True)

organizes numbers from high to low

if strings, goes in reverse alphabetical order

dictionary

a list, but more general. in {}. index dont have to be integers

key value pair

key- the “words” of the dictionary

value- the “meanings” of the words

aka as an item

creating a dictionary

dict()

or {} to a variable

adding items to a dictionary

dictname[newkey]=newvalue

keys can be….

strings or numbers

and CANNOT be repeated, will just update to the “last” instance

values can be…

any data type: strings, integers, floats, lists, dict, bool

duplicated as well!

accessing values in a dictionary

two methods

1. dictname[keyname] also used for strings and list

2. dictname.get(keyname) only for dict

   can get all values with, returns none if not there

3. d.values()

traversing through keys of a dict in a loop

for key in dict:

print(key)

traversing through values of a dict in a loop, 2 methods

1. for variable in dictname:

   print(dictname[variable]

2. for variable in dictname.values():

   print(variable)

traversing through items/key value pairs in a loop. 3 methods

1. for variable in dict:

   print(variable, dict[variable])

2. for variable in dict.items():

   print(name)

   will return each as tuple

3. for k,v in dict.items():

   print(k, ";”, v)