Module 2 - Variables, expressions and statements

Question 1

T or F: Programs must be designed before they are written

Answer 1

True

You must write down the steps (pseudo code, flowchart)

Question 2

Algorithm

Answer 2

Set of well-defined logical steps that must be taken to perform a task

Question 3

What do the following mean in a flowchart?

Oval, rectangle, parallelogram

Answer 3

Oval = "terminal" = start or end
Rectangle = process 
Parallelogram = input/output

Question 4

What is the input function in Python? Give an example.

Answer 4

variable = input(prompt)

This statement assigns the input to a variable, the prompt is what the user sees and what prompts her to input data
For example,
age= input(“Enter your age”)
This assigns the user’s input of their age to the variable named “age”

Question 5

Input function returns what data type? How do you change that?

Answer 5

String
Add int() before input: 
variable=int(input("enter your age"))

Question 6

What is a function?

Answer 6

A piece of code that performs an operation
A function is a set of statements that take inputs, do some specific computation and produces output. The idea is to put some commonly or repeatedly done task together and make a function, so that instead of writing the same code again and again for different inputs, we can call the function

Question 7

T or F - Python is case sensitive

Answer 7

True - it is cAsE sEnSitiVE!

Question 8

Variable

Answer 8

A location in RAM

Values used in a program are stored in and retrieved from the memory unit. In High-level languages, symbolic names are used in place of actual memory addresses. These symbolic names used in this manner are called Variables

Question 9

What are the three main data types?

Answer 9

Integer = int() = whole numbers
Float = float() = numbers with decimals 
String = str() = letters

Question 10

Can a variable be enclosed in quotes? For example, “salary” = 45

Answer 10

No!

“Salary” is a string

Question 11

Variable naming rules

Answer 11

• cannot be a python keyword
• first character must be a letter or an underscore
• after first letter, can only use letters, numbers and underscores
• case sensitive

Question 12

What is an expression? Give some examples

Answer 12

Any combination of variables, operations, and values that yields a result
(Also: anything that requires simplification)
Examples:
input(“type your name”)
int(“45”)
2+2

Question 13

What is a string literal?

Answer 13

Anything enclosed in quotes

Examples: “hello”, “42” “23.3”

Question 14

If you perform a math operation to the following data type operands, what is the resulting data type?
int, int
float, float
int, float

Answer 14

intint = int
floatfloat=float
int*float=float (int is temporarily converted to float for this expression)

Question 15

What happens when you convert float to int data type? For example, 3.9999 to int?

Answer 15

Decimal is chopped off, it is NOT rounded

3.9999 becomes 3

Question 16

How do you display multiple items with a single print function? How are they displayed?

Answer 16

Separate arguments with a comma: print(a,b)

Arguments are displayed in the order they are passed to the function, results are separated by a space

Question 17

How do you break long statements into multiple lines?

Answer 17

use \ character

For example,
print(“yas”,\
“why not”)

Question 18

What is the end of a print function? How do you change that?

Answer 18

The end of a print function is the newline character (the backslash which tells the program to start a new line after the print function)
There’s a special argument called end=’delimiter’ that will place the delimiter you specify instead of the newline character

Question 19

What is the item separator when items are displayed in a print function? How do you change that? For example, change to new line

Answer 19

Space
Special argument sep=’delimiter’
print(“yes”,”why not”,sep=’\n’)

Question 20

What is \n? What is \t?

Answer 20

Special characters in a string literal, they are commands embedded in a string
Represents new line and horizontal tab

Question 21

How do you format display of numbers on screen?

Answer 21

Use format function, which has two arguments: numeric value to be formatted and format specifier
Returns string containing formatted number

Question 22

What does the format specifier typically include?

Answer 22

Precision and data type

can indicate scientific notation, comma separators, and the minimum field width used to display the value

Question 23

What do the + and * operators do on strings?
For example, “apples”+”oranges”
“Spam”*3

Answer 23

Concatenate and multiply, respectively:
applesoranges
SpamSpamSpam

Question 24

What are the three types of errors when debugging?

Answer 24

1. Syntax - structure and rules, Python can’t understand what you are saying
2. Runtime - aka exceptions, occur after the program starts running, Python understands what you’re saying but runs into an error when executing
3. Semantic errors - program runs without error messages but doesn’t do what you want

Question 25

Assign the average of the values in the variables a, b, and c to a variable avg. Assume that the variables a, b, and c have already been assigned a value, but do not assume that the values are all floating-point. The average should be a floating-point value.

Answer 25

avg=(a+b+c)/3

/ will always result in a float
typically, you would need to convert one of the variables (a,b,or c) to float to have the result as a float, but not this time b/c because / always results in a float

Question 26

Write a print statement to show “Hello” and “ World” separated by: 1. a new line

Answer 26

print(“Hello \nWorld”)