Chap 8 - programing (python) - conditions, loops, string manipulation, arrays

Question 1

commenting on code

Answer 1

this symbol must be added for each line of comment

Question 2

rules for variables

Answer 2

-has to start with a character
-no special char and spaces - will change program (except underscore)
-case sensitive
Poop & poop are 2 diff variables

Question 3

note: explain each thing when explaining assignment

Answer 3

eg. c = a + b
- c: variable
- +: addition of a and b
- =: assignment of variable

Question 4

name 6 data types in python

Answer 4

-integer
-string
-boolean
-float
-character (char)
-date

Question 5

features of data types

Answer 5

-all chars are strings, not all strings are chars
-integer be stored in float because it requires less memory than float. it cannot work the other way around
-integer & float can be stored as string but lose their properties = can’t do mathematical operations on them, string cannot be stored in integer or float

Question 6

how do you find input for diff data types

Answer 6

str(input(“ “))
int(input(“ “))
float(input(“ “))

Question 7

print function

Answer 7

print(“ “)

Question 8

how to print i in a single line in a loop

Answer 8

print( i, end=” “)

Question 9

2 ways you can print multiple messages on print function

Answer 9

-comma btw words
-concatenation (adding) = join tgt only strings using +
(space in comma, no space in concatenation)

Question 10

what does \t do

Answer 10

a tab of space

Question 11

what does \n do

Answer 11

a new line

Question 12

what must you put when using \t and \n

Answer 12

quotations because they’re strings

Question 13

arithmetic operation for
-addition
-subtraction
-multiply
-divide
-remainder
-power
-squared

Answer 13

• +
• -
• *
• / (float), // (integer)
• %
• **
• **(1/2)

Question 14

relational operation for:
-greater than
-greater than or equal
-smaller than
-smaller than or equal
-equal (comparison)
-not equal (comparison)

Answer 14

• >
• > =
• <
• <=
• ==
• !=

Question 15

difference btw = & ==

Answer 15

= - assignment of variable
== - comparison

Question 16

logical operators in conditions

Answer 16

• and
• or
• not
  eg. if not hungry:

Question 17

and & or conditional statements

Answer 17

eg. if ( age> 10 and age< 20):
eg. if ( age> 10 or age< 20):

Question 18

conditional statement to get something in between value

Answer 18

eg. if (0 < username <10):

Question 19

when checking for discounts, always put bigger no. first

Answer 19

if total > 1000;
discount = total *0.2
elif total > 500:
discount = total *0.1

Question 20

if, elif, else conditional statement

Answer 20

if ( ):
action
-indentation
elif ( ):
action
-indentation
else:
action
-indentation

Question 21

nested ifs

Answer 21

if ( ):
if ( ):
-indentation

Question 22

match case statements

Answer 22

match (variable):
case “something”:
action
case _:
action (only run when none of others match)
-use like if statements

Question 23

use of loops

Answer 23

use same algorithm for diff. inputs

Question 24

types of loops

Answer 24

-for (count controlled) - knows how many times to run - doesn’t check condition
-while (pre condition) - checks iterating value before running - use for validation

Question 25

basic structure of loops

Answer 25

-initializer- variable which controls if loop is done or not -action -stopping condition -updating counter/ no. loops

Question 26

for loop

Answer 26

-for i in range (__,__,_if you want__): -for i in (variable/ list/ str) = (i changed to elements in variable/ list/ str) -third one changes the steps between the loop -don't need to initialize iterating variable at start (auto counter update)

Question 27

how does range function work

Answer 27

eg, (0, 5) - no.s - 0, 1, 2, 3, 4 (last value not counted) - total 5 (0, 20, 2) - no.s 0-19, with 2 step in btw (eg, 0, 2, 4...) (variable/ list/ str) = no.s in that variable, list

Question 28

error in range of loops

Answer 28

-for i in range (10, lengthData+10): = i starts from 10th index - if range i beyond elements in list = index out of range error -for i in range (0, lengthData): = i starts from 0th index

Question 29

what happens if index is too big

Answer 29

index out of range error

Question 30

while loop

Answer 30

i = 0 while (_condition_): i +=1 -initialize iterating variable at start (manual counter update)

Question 31

update counter

Answer 31

i = i+1 i +=1

Question 32

how to do nested for loops

Answer 32

-2 counters for inner and outer loops -outer loop only loops after inner loop is finished eg. for j in range (0,3): for i in range (0,2): action

Question 33

types of loop control statements

Answer 33

-break -continue -pass

Question 34

break loop control

Answer 34

-write break within loop -stop loop -if used in nested loop, it stop the inner most loop

Question 35

pass loop control

Answer 35

-write pass within loop -acts as a placeholder and doesn't print the i for that loop

Question 36

loop/if/elif with a list as its range

Answer 36

n= ["A", "B"] -for i in n: -while i in n: -if variable[i] in n: note: i changes to elements in list, list can be any data type

Question 37

len function

Answer 37

-finds no. elements in a list - list can be of any data types n = [1,2,3] length = len(n) print(length)

Question 38

index values in list

Answer 38

-all char has an index value -first element = 0 - positive -last element = -1 - negative -space also has an index value

Question 39

extract a certain char from a list (string manupilation)

Answer 39

num = [6, 7, 8, 9] -print(num[ 0 ]) = 6 -print(num[ 0: ]) = 6, 7, 8, 9 -print(num[ 0:2]) = 6, 7 (index after : not included) -print(num[:2]) = 6, 7 (index after : not included) -print(num[-1]) = 9 -print(num[i:i+ n ]) = value with i index & n no.s after it

Question 40

define array

Answer 40

-a sequence of elements of the same data type -each element has an index value -arrays cannot be implemented on python so just think of them like list with 1 data type

Question 41

name of index value of first & last element

Answer 41

first - lower bound last - upper bound

Question 42

create a blank 1D array

Answer 42

-reserving memory in ram -variable = [ None ] * (number of times)

Question 43

searching algorithm - linear search

Answer 43

-compare target value with elements from left to right until they match (can be used for sorted or unsorted list)

Question 44

code for linear search

Answer 44

for i in range (len(array)): if array[ i ] == number: print("number found")

Question 45

sorting algorithm - bubble sort

Answer 45

-start with 1 chosen element -compares adjacent elements to the chosen element and swaps them if needed until it is no longer needed -use a temporary value to swap elements

Question 46

Code for bubble sort

Answer 46

n = len(array) for i in range(n - 1): for j in range(n - i - 1): if array[ j ] > array[ j + 1 ]: temp = array[ j ] array[ j ] = array[ j + 1] array[ j + 1] = temp

Question 47

swap elements with a temporary variable

Answer 47

a = 5 b = 10 temp = 0 ------------------------ temp = a a = b b = temp

Question 48

swap elements without a temporary variable

Answer 48

-ages [i], ages [i+1] = ages [i+1], ages [i] 1 2 2 1 Left to right: 1 goes to 2 2 goes to 1

Question 49

difference btw 1D & 2D array in terms of memory

Answer 49

1D - data is stored randomly in memory cell = more comparisons to find them 2D - data is stored consecutively in memory cell = less comparisons to find them

Question 50

what is a 2D list

Answer 50

a list made up of lists eg. meats = ["chicken", "fish", "turkey"] groceries = [fruits, groceries, meats]

Question 51

note: before making 2D array - make a table look alike of it mark row = 1, column = 2

Question 52

order of row & column in 2D array when: 1)creating array 2)printing array 3)traversing mark row = 1, column = 2

Answer 52

1) column, row 2, 1 2) row, column 1, 2 3) row, column 1, 2

Question 53

how to create empty 2D array

Answer 53

array = [ [ 0 for column in range ( , )] for row in range ( , )] -can replace 0 with None or " string" to fill in the blank array

Question 54

how to use a 2D list with variables to print row or element

Answer 54

for a row: -print(groceries [row]) for a single element: -print(groceries [row] [column]) -each list is a row, each element is in a column (like a table)

Question 55

traversing - accessing individual elements in 2D array

Answer 55

groceries = [["apple", "orange", "banana", "coconut"], ["celery", "carrots", "potatoes"], ["chicken", "fish", "turkey"]] -for j in groceries: for i in j: print(i) -for row in range ( , ): for column in range ( , ): print(groceries [row] [column]) -finish inner loop before changing outer loop row, column: 0, 0 0, 1 1, 0 1, 1

Question 56

code for sum of reach row in 2D array

Answer 56

for row in range ( , ): sum = 0 for column in range( , ): sum += array[row] [column] print(sum)

Question 57

code to put highest/ lowest/ avg value from 2D array in 1D array

Answer 57

highest_stores = [0 for i in range( )] salary = [[0 for c in range( )] for r in range( )] for r in range ( , ): highest_salary = salary[r] [c] for c in range ( , ): if salary[r] [c] > highest_salary: highest_salary = salary[r] [c] highest_stores[r] = highest_salary print("Highest salary in", r, "is", highest_salary[r]) -declare the first element in each row as highest salary & compare it with others -if others are bigger, highest salary is replaced by it

Question 58

how to randomly choose an element

Answer 58

import random random.choice( ) random.randint( ) / random.randstr ( ) / random.randfloat ( )

Question 59

how to add time

Answer 59

import time time.sleep( ) -in seconds

Question 60

difference between for i in range ( , ) & for i in array when comparing & printing Found/ Not found

Answer 60

for i in range ( , ): -print Found/ Not found as many times as range for i in array: -print Found/ Not found 1 time

Question 61

help for arrays: https://docs.google.com/document/d/1b5Tt-2W5yVyTZYWSwUQk3DXtFnfM_McnkaAZX1FV1QQ/edit?tab=t.0#heading=h.isd4beaopm41

Question 62

How does a post condition loop work (not used in python)

Answer 62

-initialize loop counter -execute action -update counter -check condition -if condition met, stop else repeat

Question 63

built in functions

Answer 63

1) len(_list_) - no. of element in list 2) variable.upper ( ) - all string will be uppercase 3) variable.lower ( ) - all string will be lowercase 4) pow (base, exponent) 5) round (number, decimal place) 6) import random random.choice( ) random.randint( ) / random.randstr ( ) / random.randfloat ( ) 7) import time time.sleep( )