CS 10 Test #2 Notes

Question 1

How do quotes work for python

Answer 1

You can do print(“value”) or print(‘value’) (no semicolons)

If you want to print ‘Hello’, you cannot do it like print(‘ ‘Hello’ ‘) because Python thinks that from ‘ to ‘, is what is only being printed

Question 2

How to use comments?

Answer 2

You can just do #

Question 3

How do you assign a value in Python?

Answer 3

You can just do variableName = value, no need for semicolon or putting the type of the variable

Question 4

How do you reassign values?

Answer 4

Lets say you declare a value
value3 = 3
#You have to declare what a variable is equal to in python
and then if value1 = 6, you can reassign the value
value1 = value3
now value1 is equal to 3
print(value1)

Question 5

USE GPT FOR PRACTICE QUESTIONS ON EVERYTHING YOU LEARNED

Answer 5

ok

Question 6

Are Python values fixed?

Answer 6

No they are not. For example, if you have a value
value1 = 3
you can reassign the value with a string
value1 = “hello”
and print it out that way

Question 7

How do you do mathematical operations in Python?

Answer 7

You just do it normally, so for example:
total = 0
value1 = 2
value2 = 3
total = value1 + value2
average = 0
average = (value1 + value2)/2

Question 8

What happens if you do 10 = num

Answer 8

This is a syntax error

Question 9

How do you output values with strings?

Answer 9

you can do print(“This is value1”, value1)
assume value1 is equal to 3, and there’s automatically a space between the two

Question 10

Is there always a newline between the print statements?

Answer 10

Yes there is

Question 11

How do you take a users input?

Answer 11

You do
value1 = int(input(“What is a value that you want to input?))
Also, it is always automatically a string value unless you don’t specificy the type(no matter whether it’s letters or integers)

Question 12

what does int() do?

Answer 12

It just rounds down a number(if it’s a decimal)

Question 13

What can’t you name your variables in Python?

Answer 13

The general rules are:
It can’t contain spaces
It can’t have numbers at the start(must have lowercase letters or uppercase letters, or underscores)

Question 14

what is the difference between a float and an integer value?

Answer 14

a float is a decimal whereas an integer value is a whole number

Question 15

What are different operations that you can do in Python for a variable?

Answer 15

You can do addition, subtration, multiplication, for division it actually depends on the type, as you can round it down if you do //, but you can keep it a decimal if you do /. For exponents, you do the * sign twice, and for remainder it’s %

Question 16

% means mod, returns the remainder of a value

for example:
value1 = 3;
value1 = 8 % 3
#value1 is now equal to 2

Answer 16

OK BRO

Question 17

// is integer division, / is float division

Answer 17

ok, there’s always a float number that is returned, and for integer division is it always rounded down(not up)

Question 18

3 / 4 / 2 is equal to 0.75 / 2 equal to 0.375, whereas exponents are solved from right to left. like this 2 ** 2 ** 4 is not 256, it’s 2 ** 8 = 256

Answer 18

ok

Question 19

3 + 6 * 5 * 5 ** 2 ** 3
3 + 6 * 5 * 5 ** 8
3 + 6 * 5 * 390625
11718750 + 3
11718753

Answer 19

ok

Question 20

what does +x and -x mean

Answer 20

if x is a negative value, +x makes it positive (BUT DOES NOT ALTER THE VALUE ITSELF, IT JUST HAS A RETURN TYPE OF POSITIVE)
You can also store this value into another variable
For example

Question 21

What does ~x mean?

Answer 21

It inverses the binary value of the number (review binary stuff it’s legit CSP)

Question 22

if you have a value:
x = 1
What does -x and +x called?

Answer 22

Unary minus and unary plus

Question 23

What is integer division called?

Answer 23

Floor division

Question 24

Review the second page of Lesson 6

Answer 24

OK

Question 25

((year % 4) == 0 and (year % 100) != 0) or (year % 400 == 0)

Question 26

Can you add values of different types?

Answer 26

No you can’t lmao, you can add strings and numbers by having a string integer value

Question 27

What are other ways to express multiplication

Answer 27

You can use parenthesis (3)(6), or just have variables times numbers or variables times variables by putting them right next to each other
4xy
xy

Question 28

So when using -x and +x, and int(variableName) and float(variableName), there is only a return type, and the original values of the variable are not changed, so it’s easy to store a value inside of a variable

Answer 28

K

Question 28

How to use the format specifier?

Answer 28

You know how when you are printing a variable, it is like
print(“This is the value”, value1)
And there is a space automatically right next to the string
You use the format specifier in the same way like
printformat((1234567.8973, ‘.2f’))
(the print value is an integer, it is not covered in strings, otherwise it won’t work
this will print out
1234567.89
You will have to use the format function btw to do this

Question 29

How do you add commas to what you want to print?

Answer 29

You would do:
print(format(123456.8973, ‘,.2f’))
this would print out
123,56.89

You can also do this without precision
print(format(1234567.34567, ‘,f’))
would print out
1,234,567.34567

Question 30

It is usually six digits printed after the decimal point that is the default

Answer 30

ok

Question 31

Review width specifer

Answer 31

Ok

Question 32

Let’s say a value is equal to 123456.78910, how would you print out The value is 123,456.7

Answer 32

value1 = 123456.78910
print(“The value is”, format(value1, ‘,.1f))

Actually, the .f rounds up, so it have an ending value of 8 instead of 7

Question 33

How do you use the format method for integers, not decimals?

Answer 33

if you were to print out

print(“The value is” , format(1234567, ‘10,d’))
It would print out
The value is (two spaces(one is already there due to the comma))1,234,567

Question 34

The comma counts as a placement

Answer 34

Ok

Question 35

There is always a maximum of six digits after the decimal place

Answer 35

OK

Question 36

What happens if you include percentage sign with this?

Answer 36

print(format(0.5, ‘.2%’))
would print out
%50.00

Question 37

How to have no newline when printing out values?

Question 38

Answers the practice questions from Chat GPT

Answer 38

ok

Question 39

How does an if statement work?

Answer 39

An if statement works by having a boolean statement, and if it’s true the statements below will run, otherwise the decision statement will be skipped itself

Question 40

In Python, for an if statement you do not need brackets, instead you need a colon right after the parenthesis, what is an example below of this?

Answer 40

If (value1 > 100):

value2 = value1
value = value1 + 1

Question 41

What are some operational things for boolean?

Answer 41

== means if it’s equal
if (x <= y):
#statements

if(x >= y):
#statements

if(x != y):
#statements

Question 42

You can also use the not operator in Python, what is an example of this?

Answer 42

if not(value1 < 100):
print(“Value1 is greater than or equal to 100”)
#essentially, you just reverse whatever is inside of the parenthesis

Question 43

Instead of saying && and ||, we use and and or to say those for boolean operations

Answer 43

OK

Question 44

How do you format if else statements?

Answer 44

You do:
if condition:
#statements
else:
#instead these statements will run if the boolean statement above is false

Question 45

What are nested if statements?

Answer 45

It’s when you have if and else statements within each other, if you want to do the grade thing using nested statements, you would do the code

Question 46

What are elif statements?

Answer 46

This is in replacement of nested if statements, and essentially means (else if)

Question 47

You can also do comparison with strings, for example:

Answer 47

string1 = “Value1”
string2 = “Value1”
if (string1 == string2):
print(“These two variables are equal to each other)
else:
print(“There are not equal”)

Question 48

How are string variables stored in Python?

Answer 48

They are stored by ASCII (this is on the cheat sheet, along with the format thing you have to answer GPT questions to make sure you memorized those)

Question 49

How does randint and randrange work?

Answer 49

You would have to code “import random” at the top of your code in order to include the random module. So if you do that and do
value1 = random.randint(1, 6)
this includes both 1 and 6, whereas if you do randrange
value1 = random.randrange(1, 6)
it’s between 1 and 5(the end point is not inclusive)
You can also do this with randrange
random.randrange(0, 101, 10)
This takes values at intervals but never reaches or goes past 101(the default intervals is by 1s)
so 0, 10, 20, 30, 40… 100(doesn’t go past this)
random.randrange(10)
1, 2, 3, 4, 5, 6, 7, 8, 9(doesn’t go past this)

Question 50

So just to review, to access the random module, you would do

import random

and randrange does include the starting value but not the ending value, while randint includes both, and you can also do this with randrange(10), which automatically has the intervals from 1 to 9, and you can also do randrange(1, 105, 5), which gets values 1, 6, 11, …(but if you want to get values in between 0-100, you would have to do randrange(0, 105, 5)
The starting value is always 0, btw, not 1

Answer 50

Ok lmao

Question 51

What are the two types of loops in Python?

Answer 51

Condition controlled while loop and counter controlled for loop

Question 52

How is a while loop formatted?

Answer 52

There is also a colon after the statement (like an if statement)
while value1 < 10:
#statements

Question 53

What are some shortcuts that you can do for operations?

Answer 53

x+=5 = x = x + 5
y-=2 = y = y - 2
z*=10 = z = z * 10
a/=2 = a = a / 2
c%=3 = c = c % 3

(usually it is backwards from what you think from Java)

Question 54

How would you format for loops?

Answer 54

You do
for i in range(5):
#statements

basically, i starts at 0, and goes through intervals of 1, and so once the first series of statements goes through, the value of i increases by 1 so it is now equal to 1, and the next series of statements runs (it never hits the range)

Question 55

What is another way you can format a for loop?

Answer 55

You can use brackets, as you can do:
for value in [1, 2, 3, 4, 5]
value will first start with equaling to 1, and as the for loop goes through it increases by 1, you can also not do it in order, so it’s like
for value in [1, 6, 5, 3]

Question 56

What is an easy way to memorize the maximum range?

Answer 56

For randrange and for i in range, it starts at 0, and then it NEVER hits the value(it is either 1 away or something like that based on the intervals)

Question 57

So the two ways to format for loops are
for num in [(number list)]:
and also
for i in range(5):
i starts at 0, and goes through 1, 2, 3 and then 4(never reaches 5, similar to randrange)

Question 58

You can also adjust the value of for i in range, like this (for i in range(1, 5), still it will never hit 5)

Answer 58

ok

Question 59

You can also adjust how the intervals are, how do you do this

Answer 59

for i in range(1, 10, 5)

in this case, it will start at 1, then go to 6, but won’t hit 11

Question 60

\t is essentially a tab, and it creates a bigger space than normal

Answer 60

ok

Question 61

print() essentially just creates a newline

Answer 61

ok

Question 62

So essentially, randint and for num in [(number list)] includes all of the numbers, and randrange and for i in range(value) does not include all of them(does not include the ending point

randrange(0, 101, 5)
this doesn’t include 101
for i in range(5) (0, 1, 2, 3, 4)

Answer 62

OKOK