Python Workshop

Welcome to lesson 2 of this python workshop

What will we be doing today

Do more practices to get you familar with coding

Introduce new concepts like while loop and dictionary

Some interesting things that you can do with python

Warm up and recap

Try to figure out what the following outputs before you run the code to check

Q1 : Final Score Calculator

Let's write some Python code that helps you calculate your final cumulative score for a course titled "Introduction to University Life".

This course has several assessments. For each assessment, there is a total score, which is the maximum score you could achieve for that assessment. Each assessment counts towards a certain percentage of the final cumulative score. The final cumulative score is on a scale of [0 - 100].

The assessments of this course are shown below:

Assignments:

Assignment 1: (total score 10 marks), 10%
Assignment 2: (total score 10 marks), 10%
Assignment 3: (total score 10 marks), 10%

Tests:

Test 1: (total score 30 marks), 15%
Test 2: (total score 40 marks), 20%
Exam: (total score 140 marks), 35%

For example, Test 1 is 30 marks in total and counts towards 15% of your final score. If your raw score for Test 1 is 20 marks, it is two thirds of the total score for Test 1 and it will contribute 10 marks (which is two thirds of 15) to your final cumulative score.

Your code should produce the following sample output:


# #########################
# Write your code below:
# #########################
A1 = float(input("What's your score for Assignment 1?"))
A2 = float(input("What's your score for Assigment 2?"))
A3 = float(input("What's your score for Assignment 3?"))
T1 = float(input("What's your score for Test 1?"))
T2 = float(input("What's your score for Test 2?"))
EX = float(input("What's your score for the exam?"))

final= ((A1+A2+A3) + (15*(T1/30)) + (20*(T2/40)) + (35*(EX/140)))

print("Your final cumulative score is " + str(final) + "/100")

Q2: Currency

If you visit the United States, you'll need to get familiar with their currency and the various coins and notes in circulation. Look at this link to find out more about their various coins and notes: http://www.immihelp.com/newcomer/usa-currency-coins.html

Here's a list of common coins:

Penny - 1 cent

Nickle - 5 cents

Dime - 10 cents

Quarter - 25 cents

And the commonly used notes are : $1, $5, $10 and $20 notes.

Let's write some Python code that prompts the user for an amount to pay (in US$) and that helps him/her to know how many coins or notes he/she has to provide in each denomination, to provide the exact change.Some starting code is already given to you (which takes care of the conversion pricision from float to int - you can ignore ).

Your code should produce the following sample output:


#Q2 #########
 
amount = float(input("Enter payment amount (US$) :"))
 
# ################################
# Write your code below:
# ################################
money_list = [20,10,5,1,0.25,0.1,0.05,0.01]
num_list = []

for value in money_list:
  num = amount // value
  num_list.append(num)
  amount = round(amount%value,2)
print("You need to give:" + '\n'+
      str(num_list[0]) + " 20 dollar notes" +'\n'+
      str (num_list[1]) + " 10 dollar notes" + '\n'+
      str(num_list[2]) + " 5 dollar notes" +'\n'+
      str(num_list[3])  + " 1 dollar notes"+ '\n'+
      str (num_list[4]) + " quarter coins" + '\n'+
      str (num_list[5]) + " dime coins" + '\n'+
      str (num_list[6]) +" nickle coins" + '\n'+
      str (num_list[7]) + " penny coins")


You need to give:
7.0 20 dollar notes
1.0 10 dollar notes
1.0 5 dollar notes
2.0 1 dollar notes
3.0 quarter coins
1.0 dime coins
0.0 nickle coins
4.0 penny coins

For loops and if else statements

for Loops

(Top) A for loop acts as an iterator in Python; it goes through items that are in a sequence or any other iterable item. Objects that we've learned about that we can iterate over include strings, lists, tuples, and even built-in iterables for dictionaries, such as keys or values.

We've already seen the for statement a little bit in past lectures but now let's formalize our understanding.

Here's the general format for a for loop in Python:


for item in object:
    statements to do stuff

if, elif, else Statements

if Statements in Python allows us to tell the computer to perform alternative actions based on a certain set of results.

Syntax:


if case1:
    perform action1
elif case2:     #if case 1 not true but case 2 is true, perform action two
    perform action2
else:
    perform action3

Q3: Ciphertext

Ciphertext is a result of encryption performed on plaintext using a algorithm, inorder for you to encode and decode a ciphertext you need a key.

How the encryption work: you have a string from a-z and for all the letters in the key, you take out these letters from the string and place it at the back of the string to give you a different series of 26 characters. Then you map whatever that is in the text from the first string to the second string

Part 1 [ ** ]: Implement a function called cipher_text that takes in the following parameters:

`text`: the text to be encrypted

`key`: the key used to encrypt the text

and returns the encrypted text

For example, The text is i love sutd, the key is apple then the second string will be bcdfghijkmnoqrstuvwxyzaple Then you compare the first string, the second string and the text. i is at position 8 of the first string and hence it should be replace by the character at position 8 of the second string which is k so on and in the end you will get a encrypted text k oszg wyxf

You may find the function string.index(ch) useful, it reutrns you the position of ch in the string, this works with a list also


def cipher_text(text,key): #can break down into smaller functions 
  first_string = 'abcdefghijklmnopqrstuvwxyz'
  second_string = ''
  unique_ch = ''
  for ch in first_string:
    if ch not in key:
      second_string += ch
    else:
      unique_ch += ch
  second_string += unique_ch
          
  encrypted_text = ''
  for ch in text:
      if ch == ' ':
          encrypted_text += ' '
      else:
          pos = first_string.index(ch)
          encrypted_text += second_string[pos]
  return encrypted_text

Part 2 [ ** ] : Those of you who are interested or faster than the rest can try to implement a function called decipher_text to convert the encrypted message into normal language.

Dictionary

Dictionary is a structure in python just like list. Both are mutable, dynamic(no fix size) and can be nestd

For dictionary there are only 2 things to note

value

The data that is stored in dictionary is always a key-value pair.

You can access the value of a pair via the key.

Dictionary is very uesful for database creation and packaging of data and transmit it. ie: transmitting user details from the server to the website frontend.

Some basic syntax


#declaring
my_dict = {}


#a dictionary can hold differnt kind of data
my_dict['another_dict'] = {'key_one':'value_one','key_two':'value_two'}
print(my_dict['another_dict'])


my_dict['a_list'] = ['a','b','c','d']
print(my_dict['a_list'])


#accessing all the key and values in a dictionary
for key in my_dict.keys():
  print(key)


for value in my_dict.values():
  print(value)


for key,value in my_dict.items():
  print(key,value)


#Sorting a dictionary
test_dict = {1:'a',53:'a',15:'e',3:'q',63:'q',4:'k',24:'s',14:'r',3:'c'}


#By their keys
print(sorted(test_dict.items()))

How to sort a dictionary by their values

Now that we know how to sort the dictionary by their keys, how do we do so for values?

code your own logic that outputs a sorted version of the dictionary


#By their values

sorted_dict = {}# create another empty dict

'''
This method is very ineffective 
since for every value in sorted list 
you have to iterate through the entire dictionary to 
find the matching key_value pair
'''
for sorted_value in sorted(test_dict.values()):     #iterate through a sorted list containing the values of the dictionary
  for key,value in test_dict.items():           #iterate through all the items in the dictionary
    if value == sorted_value:                 
      sorted_dict[key]=value
print(sorted_dict)

print(sorted(test_dict.items(),key = lambda item:item[1]))

While loop

abit similar to for loop, but it keeps running until the condition is false

the main difference between for loop and while loop is

for loop is used in situations where you know the number of iterations to go through
while loop is used in situations where you do not know the number of iterations to go through but you know what is the condition that it should stop


# Only when the condition behind the while statement is True, then only  it will enter the loop
# So do remember to update the condition for you to exit the while loop.
# Unless you want it to run forever

index = 1
while index < 5:
  print('This statement is printed {} times'.format(index))
  index += 1
print(index)


# one of the important application of while loop is to validate input from user
# prompt the user to input their gender and if its not M or F you will notify them that its wrong input and ask them to input again

# Put your code below
gender= input("What's your gender? Please enter M or F: ")
while not(gender == 'M' or gender == 'F'):
    print("Wrong input")
    gender= input("What's your gender? Please enter M or F: ")

if gender == 'M':
    print("Thanks! Your gender is male.")
    
if gender == 'F':
    print("Thanks! Your gender is female")

Q4: Number Guessing Game

Part 1 Write a piece of code that does the following:

The program first generates a random number between 1 and 100 (both inclusive). You can try to make the range to be a user inputYou can use the randrange() or randint() function from the random module to generate the number.

The program then keeps prompting the user to guess the random number generated until the user's guess is correct. When the guess is wrong, the program gives a hint about whether the guess is too low or too high.

A sample run of the program can be found below. Note that in this sample run 95 is the random number generated in the beginning.


Enter your guess (between 1 and 100) :34
Your guess is too low!

Enter your guess (between 1 and 100) :58
Your guess is too low!

Enter your guess (between 1 and 100) :73
Your guess is too low!

Enter your guess (between 1 and 100) :86
Your guess is too low!

Enter your guess (between 1 and 100) :99
Your guess is too high!

Enter your guess (between 1 and 100) :90
Your guess is too low!

Enter your guess (between 1 and 100) :95

Bingo!


# Put your code below
import random
random_value= random.randrange(1,100)
guess= int(input("Enter your guess (between 1 and 100): "))#select a random number within the range
while not (guess == random_value):#if they have not guess the value, keep the loop running
    if guess > random_value:
        print("Your guess is too high!")
        guess= int(input("Enter your guess (between 1 and 100): "))
    if guess < random_value:
        print("Your guess is too low!")
        guess= int(input("Enter your guess (between 1 and 100): "))
        
print("Bingo!")

Q4: Number Guessing Game

Part 2 Write a piece of code that does the following:

The program first generates a random number between 1 and 100 (both inclusive). You can try to make the range to be a user inputYou can use the randrange() or randint() function from the random module to generate the number.

The program then keeps prompting the user to guess the random number generated until the user's guess is correct. When the guess is wrong, the program gives a hint about whether the guess is too low or too high and keep track of the current range of valid guesses.

A sample run of the program can be found below. Note that in this sample run 95 is the random number generated in the beginning.


Enter your guess (between 1 and 100) :34
Your guess is too low!

Enter your guess (between 34 and 100) :58
Your guess is too low!

Enter your guess (between 58 and 100) :73
Your guess is too low!

Enter your guess (between 73 and 100) :86
Your guess is too low!

Enter your guess (between 86 and 100) :99
Your guess is too high!

Enter your guess (between 86 and 99) :90
Your guess is too low!

Enter your guess (between 90 and 99) :95

Bingo!


import random
#get the range from the user input
start = int(input('Enter the start of the range:'))
end = int(input('Enter the end of the range:'))

random_value= random.randrange(start,end)#select a random number within the range

guess= int(input("Enter your guess (between"+ str(start)+" and " +str(end)+ "): "))
while not (guess == random_value):#if they have not guess the value, keep the loop running
    
    if guess > random_value:
        print("Your guess is too high!")
        end = guess       #if the guess is higher than the value then change the upper bound 
        guess= int(input("Enter your guess (between"+ str(start)+" and " +str(end)+ "): "))
    
    else:
        print("Your guess is too low!")
        start = guess#if the guess is smaller than the value then change the lower bound 
        guess= int(input("Enter your guess (between"+ str(start)+" and " +str(end)+ "): "))
        
print("Bingo!")

That is all for today!!!

Hope you have fun today! If you don't understand it is ok, coding really takes some time to get yourself familiar with it.

If you are more confident in coding you can try to work on some projects using python. may help in your 1d project also

Here are some of my recommendations:

web scraping
data analysis using pandas
backend development using django or flask
telegram bot https://medium.com/ieee-manipal/build-a-telegram-bot-using-python-23b13549856f