Advanced Python Programming

Hoang-Giang Cao (高黃江)

Sep 2023

MIDTERM - Windows Programming Design

• Date: 31 March 2025
• 90 mins - On-site programing
• Topics: If-else, for loop, functions
• 6-8 coding problems

Schedule

Basic Python

What will we learn today?

• Built-in function
• User-defined function
• Variable scope

Basic Python

What will we learn today?

• What is functions
• How to define a function
• Parameters & Argument
• Keyword parameters & optional parameters
• Return type

Function

• We already use some function in python
• input() -> take input from keyboard
• print() -> print out to screen
• int() -> convert to integer number
• len() -> return the number of objects in a list
• range () -> return a list of number in a defined range
• The above functions are built-in functions in Python (內建函式)
• Originally defined within the Python (Python 內建了多種始終可用的函數)

from math import sqrt,floor, ceil, pow

​

N = 9

​

print(f"sqrt(9) \t {sqrt(N)}")

print(f"9^2 \t\t {pow(9, 2)}")

print(f"9^3 \t\t {pow(9, 3)}")

print(f"abs(-9) \t {abs(-9)}")

print(f"floor(9.2) \t {floor(9.2)}")

print(f"ceil(9.2) \t {ceil(9.2)}")\

Built-in Function - Example

• For other built-in functions, you may need to check them yourself when needed in practice

import math

​

N = 9

​

print(f"sqrt(9) \t {math.sqrt(N)}")

print(f"9^2 \t\t {math.pow(9, 2)}")

print(f"9^3 \t\t {math.pow(9, 3)}")

print(f"abs(-9) \t {abs(-9)}")

print(f"floor(9.2) \t {math.floor(9.2)}")

print(f"ceil(9.2) \t {math.ceil(9.2)}")

Not specify the function -> math.function( …)

Specify the function -> function( …)

Function

• There are 2 types: built-in function and user-defined function
• Beside the built-in function defined by Python, user can define their own functions, which called user-defined functions.

​

• Which mean, user (coder/programmer) - you, write your own function, to do some specific task

Function

In short, function is a block of code that do a specific task

Function

• So, why do we need to write our own functions?

Function

• So, why do we need to write our own functions?
• You gonna write a hundred -> a thousand lines of code.
• You should not write them all in sequence as you did so far.
• You should break the code down to smaller part, for a specific task that the block of code do.

-> So, we need to write a block of code to do a specific task in a function.

Function

• So, why do we need to write our own functions?
• Do some specific task (the task that user defined)
• Reusability: Reuse your code multiple times
• Modularity: break down complex tasks into smaller, simpler tasks.
• Readability, understandable
• Testing, debugging, maintaining
• Repeatedly using, but implementing once -> testing once, debugging once, maintaining once

Compare Python vs C++

def calculate_area_rectangle(width,length):

​

area = width * length

​

return area

​

float sum_number(int width, int length) {

float area = width * length;

​

return area;

}

• Define data type for return
• Define data type for parameters
• Not multiple return variable

• Require correct indentation
• NOT require data type (flexible)
• Allow multiple return variable

1

1

2

3

1

4

2

3

Function

• How to define a function in python

def print_welcome_messege():�

print("Hello, ")

print ("Welcome to Advance Python Programming class.")

keyword

function name

Parentheses () and colon :

小括號 & 冒號

Function

• How to define a function in python

def print_welcome_messege():�

print("Hello, ")

print ("Welcome to Advance Python Programming class.")

keyword

function name

Parentheses () and colon :

小括號 & 冒號

body

Indentation

The block of code bellow (same indentation) is belong to the function

A block of code

Function

• How to use a function -> To use a function, we call it
• Call by the function name, with parentheses () 小括號

def print_welcome_messege():�

print("Hello, ")

print ("Welcome to Advance Python Programming class.")

​

​

print_welcome_messege()

​

Call a function by function name

Function

• How to name your function?

Must:

• NOT starting by a number, or specific character like '@', '$', '!' (except underscores ‘_’)
• Starting with a character or underscores _
• Avoid using Python keywords (if ,else, for, while)
• Avoid using built-in functions name (min,max,print)

Should:

• Function named in lowercase letters
• Meaningful/descriptive -> easy to get/understand the purpose of function
• . I.e find_max_value(), remove_smallest_value(); calculate_total_price()
• Connect multiple words by underscores “_” I.e find_max_value();

Function

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses

def print_welcome_messege():�

print("Hello, ")

print ("Welcome to Advance Python Programming class.")

Parentheses () and colon :

小括號 & 冒號

Function

• Parentheses ? ->
• We place the parameters (variable inputs of the function) inside the parentheses

def print_welcome_messege(first_name,last_name):�

print("Hello,”,first_name,last_name)

print ("Welcome to Advance Python Programming class.")

Function

• Parentheses ?
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with arguments

def print_welcome_messege(first_name,last_name):�

print("Hello,”,first_name,last_name)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Allen”, “Huang”)

parameters

arguments

Function

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with arguments, in the same order as parameters

def print_welcome_messege(first_name,last_name):�

print("Hello,”,first_name,last_name)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Allen”, “Huang”)

parameters

arguments

Function

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with arguments, in the same order as parameters

def print_welcome_messege(first_name,last_name):�

print("Hello,”,first_name,last_name)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Allen”, “Huang”)

parameters

first_name = “Allen” ; last_name = “Huang”

Function

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with different arguments

def print_welcome_messege(first_name,last_name):�

print("Hello,”,first_name,last_name)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”, “Messi”)

parameters

first_name = “Lionel” ; last_name = “Messi”

Function

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with different arguments

def print_welcome_messege(first_name,last_name):�

print("Hello,”,first_name,last_name)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”, “Messi”)

print_welcome_messege("Cristiano”, “Ronaldo”)

parameters

Reuse the function with different arguments

Function

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with different arguments

def print_welcome_messege(first_name,last_name,student_id):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”, “Messi”, 10)

parameters

first_name = “Lionel” ; last_name = “Messi”; student_id = 10

We can have multiple parameters

​

Here is 3

Argument position & Optional parameters

Function

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with different arguments

def print_welcome_messege(first_name,last_name,student_id):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”, 10, “Messi”)

parameters

The argument place correspondence with the parameters

Student_id = “Messi”

Function

• Keyword: make your function readable

​

def print_welcome_messege(first_name,last_name,student_id):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege(first_name="Lionel”, last_name=“Messi”, student_id= 10)

Function

• Keyword arguments: make your function readable
• With keyword argument, you can place the arguments in any order

def print_welcome_messege(first_name,last_name,student_id):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege(student_id= 10, last_name=“Messi”, first_name="Lionel”)

Function

​

​

• Parameters: variable input of the function
• Use as local variable inside the function
• Arguments: actual value for a given parameters
• Can call function with different arguments
• Or saying assigned different value for the parameters

def print_welcome_messege(first_name,last_name,student_id):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”, “Messi”, 10)

Optional parameters

• Parentheses ? ->
• We place the parameters (inputs of the function) inside the parentheses
• We called the function with different arguments

def print_welcome_messege(first_name,last_name,student_id):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”, “Messi”)

Required parameters

first_name = “Lionel” ; last_name = “Messi”; student_id = ?!? missing argument

Missing argument

​

Getting error

Optional parameters

• Optional parameters
• Also in C/C++, Java and other programming languge

def print_welcome_messege(first_name,last_name,student_id=1):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”,“Messi”)

Optional parameters

• Optional parameters: parameters goes with default value
• Required parameter can not be missed

def print_welcome_messege(first_name,last_name,student_id=1):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”,“Messi”)

Optional parameters

Required parameters

Optional parameters

• Optional parameters must go after required parameters

def print_welcome_messege(first_name,last_name,student_id=1):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”,“Messi”)

Optional parameters

Required parameters

Optional parameters

• Optional parameters must go after required parameters
• I.e: all optional parameters must be placed at the end in the parameter list

def print_welcome_messege(first_name, student_id=1,last_name):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”,“Messi”)

Optional parameters

ERROR

Return Values

Return Types of Function

• There are 2 ways to return a function:
• Return a value or a set of values
• Do a task
• Do some calculations, and return the result

​

• Return nothing or Return None (by default)
• Do a task, NOT return anything
• If no return, means return None

Return Types of Function

def sum_number(a,b):� result = a+b

return result

​

res = sum_number (5,7)

print (res)

Do a task, calculation, and return the value

def sum_number(a,b):� result = a+b

print (result)

​

​

sum_number (5,7)

Do a task, NOT return anything

Return Types of Function

def calculate(a,b):� summation = a+b

subtraction = a-b

multiply = a * b

division = a/b

return summation, subtraction, multiply, division

​

sum,sub,mul,div = calculate(5,7)

print (“sum:”,sum)

print (“sub:”,sub)

print (“mul:”,mul)

print (“div:”,div)

Do a task, calculation, and return multiple values. to use later (assign to a variable)

Return Types of Function

def calculate(a,b):� summation = a+b

subtraction = a-b

multiply = a * b

division = a/b

return summation, subtraction, multiply, division

​

sum,sub,mul,div = calculate(5,7)

print (“sum:”,sum)

print (“sub:”,sub)

print (“mul:”,mul)

print (“div:”,div)

​

Do a task, calculation, and return multiple values. to use later (assign to a variable)

In order!

Function

• A function is a set of statements that (might) take inputs, do some specific computation, and (might) return output.
• Some function might not require any input
• Some function might not return output

Function

• Keyword return: when the return is executed, it will out of the function immediately

def sum_number(a,b):� result = a+b

return result

print (“Up to here”)

​

​

res = sum_number (5,7)

print (res)

Never reach here

Function

• Keyword return: when the return is executed, it will out of the function immediately

def print_welcome_messege(first_name,last_name,student_id):�

print("Hello,”,first_name,last_name)

print ("Your student ID:”,student_id)

return

print ("Welcome to Advance Python Programming class.")

​

print_welcome_messege("Lionel”, “Messi”, 10)

Never reach here

Function

• Why return not always placed at the end of the function?
• Because sometime you want to terminal the function earlier
• To save the time when a specific condition is reached already.

def find_the_first_odd_number(arr):

for i in range (len(arr)):

if (arr[i] %2 == 0):

return number �

print("Here, No odd number”)

return -1

x = [1,3,5,7,2,4,6,8,10]

return_value = find_the_first_odd_number(x)

print(return_value)

If reach an odd number, will return the number immediately

Function

• Why return not always placed at the end of the function?
• Because sometime you want to terminal the function earlier
• To save the time when a specific condition is reached already.

def find_the_first_odd_number(arr):

for i in range (len(arr)):

if (arr[i] %2 == 0):

return number �

print("Here, No odd number”)

return -1

x = [1,3,5,7]

return_value = find_the_first_odd_number(x)

print(return_value)

If can not any odd number, will run until the end

Compare Python vs C++

def calculate_area_rectangle(width,length):

​

area = width * length

​

return area

​

float sum_number(int width, int length) {

float area = width * length;

​

return area;

}

• Define data type for return
• Define data type for parameters
• Not multiple return variable

• Require correct indentation
• NOT require data type (flexible)
• Allow multiple return variable

def calculate(a,b):

summation = a+b

subtraction = a-b

multiply = a * b

division = a/b

return summation, subtraction, multiply, division

Compare Python vs C++

def calculate_area_rectangle(width,length):

​

area = width * length

​

return area

​

float sum_number(int width, int length) {

float area = width * length;

​

return area;

}

• Define data type for return
• Define data type for parameters
• Not multiple return variable

• Require correct indentation
• NOT require data type (flexible)
• Allow multiple return variable

1

1

2

3

1

4

2

3

Scope

Local variable, global variable, scope of variable

​

HARD TO UNDERSTAND

Scope of variable

Global variable:

• Use anywhere in the program.

​

Local variable of function:

• Use inside the function only.
• NOT available outside the function.
• If the name of local variable is the same as global variable
• Inside the function, the program will use local variable

Scope of variable

a,b,summation is local variables, can not access (not available outside the function)

def calculate(a,b):

summation = a+b

print (“inside: ”,a,b,summation)

return summation

​

sum = calculate(10, 20)

​

print (“Outside (global): ”,a,b,summation)

​

​

​

ERROR

Scope of variable

first, second is global variables, can use/access anywhere

def calculate(a,b):

summation = a+b

print (“inside f,s: ”,first, second)

return summation

​

first, second = 5, 7

sum = calculate(10, 20)

​

print (“Outside (global) f,s: ”,first, second)

​

​

​

GLOBAL

Scope of variable

If local variable has the same name with the global variable

inside the function, local variable has the priority (scope = local)

def calculate(a,b):

first, second = 1, 2

print (“inside f,s: ”,first, second)

summation = a+b

return summation

​

first, second = 5, 7

print (“Outside (global) f,s: ”,first, second)

​

sum = calculate(10, 20)

​

​

LOCAL

GLOBAL

Scope of variable

def calculate(a,b):

print ("Inside function: f, s",first, second)

print ("Inside function: a, b",a, b)

summation = a+b

return summation

​

​

first, second = 5,7

sum = calculate(first, second)

​

print ("Global: f, s",first, second)

​

​

​

Let’s make it more complicated.

Local:

first = ?

second = ?

a = ?

b = ?

Global

first = ?

second = ?

a = ?

b = ?

Scope of variable

def calculate(a,b):

print ("Inside function: f, s",first, second)

print ("Inside function: a, b",a, b)

summation = a+b

return summation

​

​

first, second = 5,7

sum = calculate(first, second)

​

print ("Global: f, s",first, second)

print ("Global: a, b",a, b)

​

​

​

Let’s make it more complicated.

Local:

first = 5

second = 7

a = 5

b = 7

summation = 12

​

Global

first = 5

second = 7

a = not available

b = not available

sum = 12

Scope of variable

def calculate(a,b):

first, second = 1,2

print ("Inside function: f, s",first, second)

print ("Inside function: a, b",a, b)

summation = a+b

return summation

​

​

first, second = 5,7

sum = calculate(first, second)

​

print ("Global: f, s",first, second)

print ("Global: a, b",a, b)

​

​

​

Let’s make it more complicated.

Local:

first = 1

second = 2

a = 5

b = 7

summation = 12

Global

first = 5

second = 7

a = not available

b = not available

sum = 12

Scope of variable

Global variable:

• Use anywhere in the program

​

Local variable of function:

• ONLY use inside the function.
• NOT available outside the function.
• If the name of local variable is the same as global variable
• Inside the function, local variable has the priority (scope = local)

Simple Examples

Exercises 1

Write function to calculate and return the area of a rectangle.

Function takes 2 floats numbers as width and lengths

area = length * width

Test case (of function):

Exercises 1

Write function to calculate and return the area of a rectangle.

Function takes 2 floats numbers as width and lengths

Test case (of function):

def calculate_area_rectangle(width,length):

​

area = width * length

​

return area

​

​

​

print(calculate_area_rectangle(2,3))

print(calculate_area_rectangle(2.5,3.5))

print(calculate_area_rectangle(10,2.5))

​

area = length * width

Exercises 2

Write a function to calculate and return the area of circle

Function takes 1 float number as radius of the circle

��

​

​

​

Test case (of function):

Exercises 3

Write a function to return the Last Digit of number a

Hint: 119 = 11x10 + 9. 91 = 9*10 + 1 -> a%10

​

​

��

​

​

​

a % b = remainder

a = b * quotient + remainder

Test case (of function):

Exercises 3b

Write a function to return the Second Digit of number a

Hint: 119 = 11x10 + 9. 119%10 = 9

int(119/10) = 11 or floor(119/10) = 11 then, 11%10 = 1

​

​

��

​

​

​

a % b = remainder

a = b * quotient + remainder

Test case (of function):

Example 4

def divide(a, b):

if b == 0:

print("Error: Division by zero is not allowed.")

return 0 # You can return a specific error code or value

return a / b

​

​

num1 = float(input("Enter first number: "))

num2 = float(input("Enter second number: "))

​

result = divide(num1, num2)

print("The result of division is:", result)

​

Write function to divide 2 variable. Check invalid divisible by 0

Example 5

Write function int fibonacci(int n) to print the first n numbers of fibonacci sequence

​

In the main function, require use enter an integer n. Then call function fibonacci

Example 5

Write function int fibonacci(int n) to print the first n numbers of fibonacci sequence

​

In the main function, require use enter an integer n. Then call function fibonacci

def fibonacci(n):

a, b = 0, 1

print("Fibonacci sequence:", end=" ")

​

for i in range(1, n+1):

print(a, end=" ")

next = a + b

a = b

b = next

print()

​

n = int(input("Enter a positive integer n: "))

fibonacci(n)

Example 6

Write function int pow_2(int a) to calculate the square of an integer number a. i.e a²

​

In the main function, require use enter an integer a. Then call function pow_2 to get the result of a²

Example 6

Write function int pow_2(int a) to calculate the square of an integer number a. i.e a²

​

In the main function, require use enter an integer a. Then call function pow_2 to get the result of a²

def pow_2(a):

return a * a # Return the square of a

​

number = int(input("Enter an integer: "))

​

result = pow_2(number)

print(f"The square of {number} is: {result}")

​

Example 7

Write function int factorial(int a) , calculate and return the result of factorial of a . ie a!

​

In the main function, require use enter an integer a. Then call function factorial to get the result of a!

Example 7

Write function int factorial(int a) , calculate and return the result of factorial of a . ie a!

​

In the main function, require use enter an integer a. Then call function factorial to get the result of a!

def factorial(a):

result = 1

for i in range(1, a + 1):

result *= i

return result

​

a = int(input("Enter an integer: "))

result = factorial(a)

​

print(f"The factorial of {a} is: {result}")

Example 8

Write function int pow_a_of_b(int a, int b) , calculate and return the result of a^b

​

In the main function, require use enter 2 integers a and b. Then call function pow_a_of_bto get the result of a^b

Example 8

Write function int pow_a_of_b(int a, int b) , calculate and return the result of a^b

​

In the main function, require use enter 2 integers a and b. Then call function pow_a_of_bto get the result of a^b

def pow_a_of_b(a, b):

result = 1

for i in range(b):

result *= a

return result

​

a = int(input("Enter the base: "))

b = int(input("Enter the exponent: "))

​

result = pow_a_of_b(a, b)

​

print(f"{a}^{b} is: {result}")

​

​

​

Example 9

Write function int sum_N(int n) , calculate and return the result of sum all number from 1 to N

In the main function, require use enter an integer n . Then call function sum_N to get the result