Python - Function Parameters (Day 8)

This is a 100 Days challenge to learn a new language (Python). 100 Days of Code - The Complete Python Pro Bootcamp 

I will post some notes to motivate myself to finish this challenge.

Function parameters and arguments

Ex:

# Define a function with some parameters

# something is called 'Parameter'

# something is a name of data which has been passing to this function,

# then we can use this name inside this function as an reference

def my_function(something):

    print(f"this is {something}")

# Call a function and pass an argument

# 123 is called 'Argument'

# 123 is a actual value of the date we are passing to

my_function(123)

Result:

this is 123

Positional V.S. Keyword Argument

Ex:

# a custom func

def my_func(name, age):

    print(f"Hello {name}. you are {age} years old")

# positional argument

# order matters

my_func("frank", 5)

# keyword argument

# order does not matters

my_func(age=5, name="frank")

Result:

Hello frank. you are 5 years old Hello frank. you are 5 years old

Challenge - Caesar Cipher

What is it? Reference

Ex:

# Caesar Cipher

# Example

# plain_text = "hello"

# shift = 5

# cipher_text = "mjqqt"

alphabet = ['a', 'b', 'c', 'd', 'e',

            'f', 'g', 'h', 'i', 'j',

            'k', 'l', 'm', 'n', 'o',

            'p', 'q', 'r', 's', 't',

            'u', 'v', 'w', 'x', 'y',

            'z']

direction = input("Type 'encode' to encrypt, type 'decode' to decrypt:\n")

text = input("Type your message:\n").lower()

shift = int(input("Type the shift number:\n"))

# Custom Func

def caesar(direction, text, shift):

    # Define a variable for returning

    result_str = ""

    # Reduce the shift number

    # For example, if shift is 26, then the cipher text and

# the raw text are the same

    shift = shift % len(alphabet)

    if direction == 'decode':

        shift *= -1

    # Loop through all letters in text

    for letter in text:

        # Calculate the new index

        new_index = alphabet.index(letter)+ shift

        if new_index <= -1:

            # Ex: index -1 => index 25

            new_index += len(alphabet)

        elif new_index >= len(alphabet):

            # Ex: index 26 => index 0

            new_index -= len(alphabet)

        # Concatenate the string from the encoded letter

        result_str += alphabet[new_index]

    print(f"Here's the {direction} result: {result_str}")

# Call a funtion to process caesar cipher

caesar(direction, text, shift)

Result:

Type 'encode' to encrypt, type 'decode' to decrypt: encode Type your message: hello Type the shift number: 5 Here's the encode result: mjqqt

Type 'encode' to encrypt, type 'decode' to decrypt: decode Type your message: mjqqt Type the shift number: 5 Here's the decode result: hello