Comp Sci Exam 2

Positional Arguments

Arguments that must be passed in the same order in which the corresponding parameters are defined

Keyword Arguments

used to specify the parameter name with values in a function call, making the order irrelevant, and MUST be written to the right of all the positional arguments

Variable Length Arguments

*args

used in combination with regular arguments and MUST be placed after all the regular arguments

Ex: def variable_sum(first_arg,*args):

Variable-Length Keyword Arguments

**kwargs

used in the parameter list to pass a variable number of keyword arguments

Local Variables

variables defined insdie a fucntion and their scope is limited to that function

Global Variables

variables outside any function and accessible throughout the program

“global” keyword

used to modify the value of a global variable by defining it

Inner (nested) Function

a function defined inside another function and dependent on the outer function calling it to execute

“nonlocal” keyword

keyword used to affect inner function by changes to the outer function

Hidden variable

if a variable with the same name as the global variable is present in the outer function the global variable or varibale in outer function

Lambda function

lambda arguments : expression

small one-line functions that does not use keywords and can take any number of arguments but only one expression

Importing modules

import module_name

to use a user-written model and can use the keyword “as” to abbreviate module name

Import Specfic elements

from module_name import func

use the keyword “from” to import specific element

if _name_ == ‘_main_’

will execute only if the module is run as a standalone script but NOT when the module is imported ti another script

used when you want a module to define reusable values/functions while also containing runnable code

Recursion

mathematical and programming concept, meaning that a function calls itself

solves a problem by breaking it down into simpler and more manageable parts

Recursion Piece One

one or more base cases; simplest cases that the function already knows how to solve

Ex: if n==0:

            return 1

Recursion Piece Two

recursive steps, slightly simpler or smaller versions of the orginal problem

Ex: return n*factorial(n-1)

Recursion Terminate

terminates when the sequence of smaller problems equals or converges to the base case

Iteration Control Statement

repetition (loops)

Iteration Repetition Involved

repeated loop body

Iteration Termination

when the loop condition fails

Iteration Performance

usually quicker than recursion

Recursion Control Statement

conditional statements (branching aka if,elif, and else)

Recursion Rpeetition Involved

repeated function calls

Recursion Performance

singnificant overhead (run time) due to repeated function calls

Accesing Characters in a String

string_name[index]

String Slices

string_name[start:step]

a segement of a string

len() function strings

reutnrs the number of characters in the string

the ‘in’ operator string

a boolean operator that takes two stirngs and returns True if the first operatorappears as substring in the second

Ex: ‘a’ in ‘banana’ → True ; ‘seed’ in ‘banana’ → False

String Compariosn == and !=

check if two strings are equal

String Comparison >,<,>=, and <=

use lexicographical comparison of strings

Lexicographical comparison

comparing string based on the order of thier elements; comparison stops at the first position where elements differ

Python String Formatting

f “string { }”

Escpae Charaters

a baclash followed by character you want to insert

can insert special characters in a string

Ex: print(“He said to me, “\How are you?\” with a smile. ”)

Quote

\’ or \”

Backlash

\\

prints a \ in a string

New Line

\n

Carriage Return

\r

overwrite the existing content on that same line from the beginning, effectively replacing the previously printed characters

Tab

\t

Backspace

\b

deletes character it follows a in string

Slice Assignment (List)

use the slice operator on the left side of an assignment to update multiple lsit elements

Deleting List Elements

use ‘del’ operator to delete one or a slice of list elements

List Operations ‘+’

The operator combines the list to form a new list

[1,2,3] + [4,5,6] → [1,2,3,4,5,6]

List Operator ‘*’

the operator returns a list that repeats the original list a given number of times

[2,4,6]*3 → [2,4,6,2,4,6,2,4,6]

len() fucntion in list

function returns the number of elements in the list

len([‘spam’,2.0,5,[10,20]])==4

min() and max()

return the min and max elements of a list respectively

will say an error if the list has an items of mixed type

sum () function list

calculates the summation of numbers in the list

sum([2.0, 5, 10, 20]) → 37.0

List updating

slice assignment meaning the orginal and updated lists are the same object

id() function and ‘is’ operator

check if two variables refer to the same object

List Comprehension

newlist = [espression for item in oldest if condition]

offers a concise syntax to create a new list based on the items of an existing list

slicing list

creates a new list

slice assingment lists

modifies the exisitng list

Multi-Dimensional Lists

list_name[row_index][column_index]

Ex: a[2][-4]==8

Multi-dimnensional list comprehension

creates a m x n matrix where m is the number of rows and n is the number of columns

Tuples

a sequence of values where values can be ANY type, values are ordered, and duplicate values are allowed

Tuple Operators Invalid

can NOT add or remove from a tuple once created and can NOT append to or extend a tuple

Tuple Operators Valid

‘+’ and ‘*’ operators

len(), sum(), max(), min() functions

compare lexicogrpahically

‘del’ 

sorted()

sort the tuple alphabetically

Tuple Assignment

can assign multiple values to multiple variables all on one line (unpacking)

Ex: (a,b,c,d) = (1,2,’xyz’,True)

List Mutability

mutable (can be modified after creation)

List Syntax

defined using square brackets [ ]

List Methods

has more built in methods (ex: append, remove)

List Use Cases

suitable for collections of items that may change

LIst Memory Usage

consumes more memroy due to flexibility

List Iteration

iteration can be slightly lower

List Performance

slower due to dynamic size and mutability

Tuple Mutability

immutable (cannot be modified after creation)

Tuple Syntax

defined using parentheses ( )

Tuple Methods

fewer built in methods

Tuple Use Cases

ideal for fixed collections of items

Tuple Memory Usage

consumes less memory due to immutability

Tuple Iteration

iteration faster due to immutability

Tuple Performance

faster due to static size and immutability

Sets

a collection of items enclosed by curly brackets { }

and are unordered so can NOT be referred to by index and duplicate vlaues are NOT allowed

Ex: fruits= {“apple”, “banana”, “cherry”}

Add Set Items

add() function to add one item to a set

update() function to add items from another set, lidt or tuple to a set

both in place changes

Delete Set Items

remove() and discard() fucntions to remove an item

Empties set

clear() function

‘del’ opetator set

deletes set completely

List to Tuple Conversion

list1=[0,1,2]

tuple(list1) → (0,1,2)

Set Conversion to other Data Structures

set() function 

Ex: x = set((“apple”, “banana”, “cherry”)) or 

n = set([0,1,2,3,4])

Set Method difference()

returns the difference between two or more sets

Set Method intersection()

returns the interaction of two oe more sets

Set Method isdisjoint()

returns whether two sets have an interaction or not

Set Method issubset()

returns whether another set contains this set or not

Set Method issuperset()

returns whether this set contains another set or not

Set Method symmetric_difference()

returns the symmetric differneces of two sets

Set Method union()

reutrns the union of sets

String Modifier :<

left aligns the result

String Modifier :>

right aligns the result

String Modifier :^

center aligns the result

String Modifier :+

use a plus sing to indicate if the result is positive or negative

String Modifier :

use a space to insert an extra space before positive numbers and aminus sign before negative numbers

String Modifier :,

use a underscore as a thousand separator

String Modifier :b

binary format

String Modifier :d

decimal format

String Modifier :e or :E

scientific format

String Modifier :f

fix point number format

String Modifier :%

percentage format

Iterable

an object that can be looped over or ‘iterated’ through one element at a time

capable of returning its member value one by one