Section 03: Variables, Values, and Math

Question 1

Define

Variable

Answer 1

Variable: Represents memory space that has a name and holds a value.

Modify through assignment statements

Question 2

Define

Assignment Statements:

Answer 2

• Assignment Statements: “Creates a new variable with a given value”
  
  • Updates → overrides old value
  • Use = for value assignment:
  Operation assigning value (not statement of equality)

What actually happens: (1) Object created ⇒ (2) Value is assigned ⇒ (3) Reference to object is stored in variable

Modify variables through assignment statements

Question 3

Define

Objects

And Object Types

Answer 3

Object Types:

1. Integer: Numbers without fraction components (Z)
2. Float: Numbers with decimals (R)
3. String: Characters or lists of characters
4. Boolean: True/False

After reassignment: old value = garbage collected (removed from memory)

Dont need to declare type with value assignment - as in Java

Life of an Object:

• Creation
• Manipulation
• Stops existing when no more reference to it (garbage collection will reclaim memory space)

Question 4

What is the purpose of temporary variables?

Answer 4

Swapping Variables: Use temporary variable → reference one values dont lose them

Ex: x = y = z = 5

Question 5

Naming Conventions

Answer 5

• Both letters and numbers; not start number
• Underscore “_” used names

Should be meaningful

Question 6

Code

Input Function

Answer 6

Ask the user to provide information

• input() pauses program execution and waits for user to type in some input from keyboard
• Once press Enter → all character typed are read & returned as strings
• New variable, name created with input

Ex: name = input('What is your name?')

Question 7

Define

Casting

Answer 7

Casting: Built-in Function to covert a value from one type to another

1. int(x): converts value x into type of int
2. float(x): convert value x into type of float
3. str(x): converts value x into type str
4. int(s, base): converts string s into type of int (Base specifies which string is)

Question 8

Arithmetic Operators

Answer 8

Arithmetic Operators: Addition (+), subtraction (-), multiplication (*), division (/), and power (**)

Others:
1. Floor Division Operator: // (rounds down to nearest whole numbers)
2. Modulus % (remainder of the floor division operator)

Question 9

String Operator

Answer 9

+ operator for string concatenation

Question 10

Define

Operands

Answer 10

Operands: values an operator acts on (literal or variables)

Question 11

Define

Expressions

Answer 11

Expressions: sequences of operands and operators

Expressions refers to a sequence of operands and Expressions, while statements are instructions express some action to be carried out

Short Circuit Evaluation: when only the first operand (line in an or statement is evaluated) then moves on with the code

Question 12

Code

What are the math functions?

Answer 12

• abs(x): returns absolute value of x
• pow(x, y): returns x^y (always a float)
• round(x): rounds x to nearest integer
• round(x, n-digits): round to given precision in decimal digit

Question 13

Math Module

Answer 13

• “File” called math module provides us with additional functions that we can use
• Access: (1) import module → import math (2) call function want to use math.function_name
  
  • sin, cos, pi

Documentation: help(math) gives documentation

Question 14

Code

import function:

Answer 14

💡 import statement gives access to functions defined in particular module

Ex: math.sqrt(x)
(not a void function)