DS 2001: Practicum 1 Warm-up: All TAs like puppies. No robots like - - PowerPoint PPT Presentation

Fall 2020 — Felix Muzny

DS 2001: Practicum 1

Warm-up:

• All TAs like puppies.
• No robots like things that TAs like.

Which of the following statements can we conclude given these two pieces of information?

• A. All robots like puppies
• B. All robots like kittens
• C. No robots like puppies
• D. No robots like kittens
• E. All TAs like kittens

Today's Computing History: The Difference Engine

Recall: Running python programs

print("Hello!") python interpreter Hello! input (executes the program)

• utput

$ python hello.py hello.py

ID IDLE

→ Atom

k

terminal

Values & Data Types

Type Examples

int

I

• 13
• too

float

1.0

• 13.3

0.72

string

" hi

"

"

cat hat

"

"12

"

boolean

True

false

Variables

Which of the following statements are true about variable declarations:

• 1. the name of the variable always goes on the right side of the "=" sign
• 2. you can use operators like "+" and "-" but only on the left side of the "=" sign
• 3. variable names may contain spaces
• 4. variable names are case insensitive
• A. 1 & 2
• B. 3
• C. 4
• D. 1, 2, & 4
• E. None of the above

Jeff

9€

NOT,

rightxty=#

Variables

• We use variables to save values of the results of expressions and functions

so that we can use them later (to print, to do further calculations, etc)

• When we declare a variable with a value, it allocates space in memory to

store this value. We can think of the variable as the "name" that it's stored under.

name = value x = 12 y = 45

x

y t

• I

The print function

• The print function is what we use to display any values or information to

the user.

# print a value print("hello") # print the value of a variable x = 47 print(x) print("hello", x) # print multiple values

print(parameters)

• print 142

)

var

# 42

string print (

" x

")

# X

P

input function

• We say that the input function returns a value (the user's input)
• To use this value, we must save it in a variable
• All values have a data type, including the return value

variable = input(prompt) name = input("What is your name? ") print("Hello!", name) print(type(name))

①

string

tix

"#

# string e.g

"12

"

functions - how to call them

return_value = function_name(arguments/parameters)

I

not always included

Type Casting

• functions that change a value from one type to another
• Each basic type has a corresponding function that changes other values to

that type. (they return the new value)

dogs = input("how many dogs? ") double_dogs = 2 * dogs print("That's so many dogs:", double_dogs)

• n

"

dogs 13J

dgE.int (dogs)

intdogs)

#

"33

"

Running python programs

Which one of these python program successfully changes ("casts") the integer value stored in the variable x to a string? A.x = string(12) B.str(x) C.x = "12" D.x = str(x)

x = 12 print(type(x)) # missing line goes here # want this to be string print(type(x))

130

O

x

• str Cx)

Reading error messages

• When you have an error, python will print out an error message. These

many *feel* like you've done something wrong, but secretly this is a great thing!

I

EOLTD End of Line

↳ End of file

Reading error messages

• When you have an error, python will print out an error message. These

many *feel* like you've done something wrong, but secretly this is a great thing!

• E

Work on your practicum - instructions on Canvas

• Remote: we're going to put you in break out rooms of 2 - 3 people.
• The TAs and myself will be moving between breakout rooms checking in
• We recommend turning on your cameras and having one person screen share

as you work through the problems

• (Remember that you will all individually turn in your assignment though!)
• Use the "ask for help" button in zoom if you have a question and there is no

TA/Felix in your breakout room.

• If your zoom crashes and you need to re-join, you'll be in the main room—we'll

keep an eye on this and re-assign you to your breakout room if this happens :)

• We'll walk through one of the problems together about 15 minutes before the

end.