Section 04: Functions and Statements

Question 1

What are the different types of operators?

Answer 1

Values and Types: Different types

Arithmetic Operators: +, -, *, /, %, //, **
- Int and float
- Expressions containing them evaluate to int/float values
- Function in math module

	**String operators**: `+, *`
- Operate on strings

Question 2

Define

Boolean Values:

Answer 2

**Either equal to True or False **

• Useful checking conditions and making options

-Takes boolean expressions as inputs and produces type of boolean

Types: not, and, or

• not: unary operator
• and, or: binary operator

Question 3

Comparison Operators

Answer 3

To compare two numbers, use the Relational Operators

Use == to compare if two numbers are equal (*= is used for value assignment)*

>>> x = 1.1 + 2.2
>>> print(x == 3.3)
#Print: False

Question 4

Define

Control Flow

Answer 4

Control flow dictates order of execution

Specific control flow statements changes order of execution

1. Which part of the code should always be executed
2. Which parts of the code should be executed only under certain circumstances
3. Which blocks of code should be executed repeatedly

Question 5

Code

(1) If Statement:

Answer 5

If Statement: list of instructions if the conditions is True

else Statement: list of instructions if the conditions is false

Question 6

Code

(2) Chained Conditionals:

Answer 6

1. if condition 1:
   List instructions to do if condition 1 is true
2. elif condition 2:
   List of instructions to do if condition 2 is true
3. else:
   List of instructions to do if both condition 1 and 2 are false

• Only one block will be executed → order matters
• The final else is optional

Question 7

Code

(3) Nested Conditionals

Answer 7

If statement within an if statement

if x == y:
print('x and y are equal')
else:
if x < y:
print('x is less than y')
else:
print('x is greater than y')

Question 8

Errors

NameError

Answer 8

NameError: Raised when local or global name is not found → only applies to unqualified names

Question 9

Errors

TypeError

Answer 9

TypeError: Raised operation or function applied to an object inappropriate type

Question 10

Errors

SyntaxError

Answer 10

SyntaxError: Raised parser encounters a syntax error

Question 11

Define

Function

Answer 11

Function: named block of code preforms task
- must be inside a module: file contains a collection of related functions
- Call a function execute code in function defintion
- Infinitely many

Input: argument

Output: return value

Ex: print(), pow(x,y), input() ...

Type: void and fruitful functions

Question 12

Define

Void Functions

Answer 12

Void Functions: functions not return a value but displays a message

Does not return a value

Why: Avoid repetition

Question 13

Define

Fruitful Functions

Answer 13

return a value

Fruitful Funcions: perform calculation then returns a result

• Ex: math.sqrt(num) returns square root of num

return value can be stored ad saved into a variable

Question 14

Code

Function Object

Answer 14

• (): parameters = have empty or not
• must indent statements to show part of the function defined

Question 15

Function Definitions

Flow of Execution

Answer 15

• Functions definitions are executed like other statements
  effect of execution is to create function object
• Statements inside a function are not executed until function is called
• Must define function → then call it

Detour: instead going to next statement, first statement of function called is executed → then go to where left off

Question 16

Define

Input Argument:

In relation to parameters

Answer 16

• Parameter not empty ⇒ has an input argument (any kind of expression)
  
  • Expression always be evaluated before being given to the function
  • Result of evaluation will be assignmed to parameter inside function
  • Arguments adds flexibility to function

Local variables: Only exist inside definition

Ex:
def function_name(input_val):
print('Some shit', input_val)

Question 17

Flow of Execution

When variable is called:

Answer 17

Variables created for each parameter
- Initialized with values provided through function call
Body of function executed

Question 18

Flow of Execution

When nothing left in body to execute

Answer 18

• All local variables are discarded
• Program goes back to line function called from

Question 19

The return statement:

Answer 19

Want create function returns value → return statement
Return: allows terminate the execution of function as soon as statement executed
- “Gives back” a value

Why use return value?

1. Allows function store output, which can be used later
2. Can save return value in a var or used fruitful functions as part of an expression

Question 20

Scope of Variables:

Answer 20

• Variable only exists inside body of the function in which it is created
• Not exist outside function

> Call ”scope” variable that part of the code which it exists

Difference between local and global variables:

1. Local Variables: Variable declared insie function’s body
   
   • Private memory space
   • Memory space allocated to input argument
2. Global Variable:

Inside a Function:

• Local variables: functions argument(s), and all other vars created in function
• Global variables: values can be accessed directly → changed through global keyword

Best Practices:

• Avoid referring global vars in functions → makes confusing

Question 21

Void Type

NonType

Answer 21

• Parity function → void type: no return value
• Void: May have input argument but no return value

Return value: None

NoneType: Used to indicate the absence of a value
- Fruitful functions those return value other than None
- Should then have at least one return statement

Question 22

Docstring:

Answer 22

Docstring: (documentation string) string write after header fo a function explain how it works

simmilar to comments but ignored by interpreter

• Use ””” or ’”

Question 23

Parts of a Docstring:

Answer 23

1. Description: what the function does
2. Type Contract: Describe type of value
3. Example: write couple of example function w corresponding return values