Few More Math Operators Just a couple of more … - PowerPoint Presentation

Slide1

Few More Math Operators

Just a couple of more … Slide2

Practice – the Metro Card

Write a program that asks the value of their current Metro Card

If each ride costs $3.75, compute:

The number of rides they have leftThe amount of money they have “left over” after previously stated given ridesThe amount of money they need to add to round out an even number of rides Slide3

Order of Operations

Python follows the order of operations (PEMDAS)

You can use parentheses inside your math expressions to group operations

Example:

x = ( (5 + 10 + 20) / 60 ) * 100Slide4

PEMDAS

Multiplication/Division, Addition/Subtraction must be done in order that it shows up, not interchangeable

3 * 4 / 2 * 5

(3 * 4) / (2 * 5) Slide5

Converting Math Formulas into Programming Statements

Most math formulas need to be converted into a format that Python can understand

Examples:

10 x y 10 * x * y

( 3 ) ( 12 ) 3 * 12

y = 3 * x / 2

 Slide6

Line Continuation

Sometimes expressions can get to be very long

You can use the “ \ ” symbol to indicate to Python that you’d like to continue the expression onto another line **

Example: x = 5 + 2 / 7 \

+ 8 – 12

This also works for the print ( ) function Slide7

Mixed Type Expressions

Python allows you to mix integers and floats when performing calculations

The result of a mixed-type expression will evaluate based on the operands used in the expression

Operand 1

Operand 2

Result

int

int

int

float

float

float

float

int

float Slide8

Exponents

You can raise any number to a power by using the “ ** ” operator

Example:

24

 2 ** 4Slide9

Division Operations

Python contains two different division operators

The “/” operator is used to calculate the floating-point result of a division operation

The “//” operator is used to calculate the integer result of a division operation, it will throw away the remainder.

*** This operation will always round DOWN.

Examples:

print ( 5 // 2 )

# 2

print ( -5 // 2 )

# -3 Slide10

Practice: Time Calculations

Ask the user to input a number of seconds as a whole number. Then express the time value inputted as combination of minutes and seconds

>> Enter seconds: 110

That’s 1 minute and 50 seconds! Slide11

Practice: Time Calculations

There’s actually an operator symbol in Python for what we just did.

Realize, that this will happen a lot. Python has functions and commands that condense the process of a common algorithm.

Let’s take a look … Slide12

Remainder Operator (modulo)

The modulo operator “ % ” returns the remainder portion of a division operation

This is basically the opposite of the “ // ” operator

Examples: 5 / 2 # 2.5

5 // 2 # 2

5 % 2 # 1 (remainder from divisor of 2) Slide13

Practice: Time Calculations

Now extend this program to include the number of hours

>> Enter seconds: 12074

That’s 3 hours, 21 minutes and 14 seconds! Slide14

Escape Key “\”

The backslash ( “ \ ” ) is known as an escape key in Python

It tells Python that the character directly following the backslash will not function in it’s regular nature

Example: print

(“This class is “

Awesome!

””)

#error!

print

(“This class is \“Awesome!\””)

>> This class is “Awesome!” Slide15

Examples of the Escape Key

We can use the escape key in various ways:

print(“

\””) # this will print a quotation mark

print(“

\n

”) # this will print a new line

print(“

\t

”) # this will print an indented tab

print(“

\\”) # this will print out a back slash Slide16

Examples of the Escape Key

print

(“We saw this

\n this will print a new line”)>> We saw this

this will print a new line Slide17

Examples of the Escape Key

print

(“We saw this

\t this will print a tab”)>> We saw this this will print a tab Slide18

Examples of the Escape Key

print

(“What if we want an actual backslash \\”)

>> What if we want an actual back slash \ Slide19

Practice: O Christmas Tree

Using a single print statement, try writing a program that prints out the image of a Christmas Tree

We want this:

>> tree /\ / \

/ \

I

I

Slide20

Examples of the Escape Key

print

(""" /

\\ \n / \\ \n

/

\\ \n

| | """)

>> tree /\

/ \

/ \

I

I Slide21

format( ) Function

This is a bit premature, but for the sake of your homework, we can use the format( ) function.

This function allows us to format numbers to as many decimal places as we’d like.

It also allows us to insert a comma every three digits, as there are in the real number system (i.e. 12,345,678) The format function must receive two arguments:

The number it is formatting (for now we’ll always pass floats)

The instructions for formatting Slide22

format( ) Function

Instructions:

format (

number , “ , . 2 f ” )

Examples:

format (

100000/7

,

“,.2f”

)

The result: 14,285.71 Slide23

format( ) Function

print ( format (

100000/7

, “,.2f” ) )>>

14,285.71

x = format(

100000/7

,

“.2f ”

)

print( “$” + x )

>>

$14,285.71 Slide24

I Woke Up in a New BugattiSlide25

Compounded Interest