# Function

def double(x):
    
    return 2 * x

double(4)

# Comment style 1

def like(stuff):
    # This function takes a string called stuff as input
    # and returns a new string that has "I like " in
    # front of the input string

    return "I like " + stuff # Here is the return statement!

like('python!')

# Comment style 2

def like(stuff):
    """ This function takes a string called stuff as input and
    returns a new string that has 'I like ' in front of the
    input string """

    return "I like " + stuff # Here is the return statement!

like('python!')

# If and else simple way

def big(x):
    """ Takes a number x as input and returns a string
    indicating whether the number is big or small. """

    if x >= 100:
        return "That is a big number!"
    else:
        return "That is a small number."
    
big(10)

# If and else smart way

def big(x):
    """ Takes a number x as input and returns a string
    indicating whether the number is big or small. """

    if x >= 100:
        return "That is a big number!"
    return "That is a small number."

big(1000)

# Chickens and Aardvarks

def a_or_an(noun):
    """ Takes a word (string) as input and returns a new string
    that adds 'a' or 'an' as appropriate. """

    if noun[0] == 'a' or noun[0] == 'e' or noun[0] == 'i' or \
        noun[0] == 'o' or noun[0] == 'u':
        return "an " + noun
    else:
        return "a " + noun
    
print(a_or_an('apple'), a_or_an('banana'))

# Silly function (elif usage, single line, param num)

def silly(x, y):
    """ This function takes two numbers as input and does
    something silly and useless. """

    if x < y:
        z = 2 * y
        return z
    elif x == y: return 3 * y
    else:
        return 0

# Variable scope, y lives inside the goofy

def goofy(x):
    y = 5
    x = x + y
    return x

print(goofy(3), y)

# Global variable, y lives in a file

y = 5

def goofy(x):
    x = x + y
    return x

print(goofy(3), y)

# Global var become local var inside a func

x = 10
def double(x):
    x = x * 2
    return x

print(double(x))
print(x)

# Some methods inside func may change muttable global var

def A(x):
    x.append(42)
    return x

l = [1, 2, 3]
print(l)
print(A(l))
print(l)

# another example

def B(x):
    x = [1, 2, 3]
    x.append(42)
    return x

l = [4, 5, 6]
print(l)
print(B(l))
print(l)

# loopy function

def loopy():
    """ This function takes no input and simply returns the sum
    of the integers between 1 and 10. """

    sum = 0 # Initialize a counter to 0
    for i in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]: # change to range(1,11) later
        sum = sum + i # update the sum, support +=, but not ++
    return sum # return the sum

loopy()

# built in sum 
print(sum([1,2,3,4]))

# define sum

def oursum(mylist):
    """ Takes a list of numbers as input and returns the sum
    of the items in that list. """

    total = 0
    for number in mylist:
        total = total + number

    return total

print(oursum([2,3,4,5]))

# count good way

def count(L, X):
    """ Takes a list and an item as input and returns the number
    of times that the item is found in the list. """

    counter = 0
    for item in L:
        if item == X:
            counter = counter + 1

    return counter

count([2,3,4,5,4,6,4,3], 4)

# count not so good way but sometimes necessary

def count(L, X):
    """ Takes a list and an item as input and returns the number
    of times that the item is found in the list. """

    counter = 0
    for i in range(0, len(L)):
        if L[i] == X:
            counter = counter + 1

    return counter

count([2,3,4,5,4,6,4,3], 4)

# func call func

def sum(mylist):
    """ Takes a list of numbers as input and returns the sum
    of the items in that list. """

    total = 0
    for number in mylist:
        total = total + number

    return total

def shoptotal(shoplist):
    """ Takes a list of lists of numbers as input and returns
    the sum of all of those numbers. """

    total = 0

    for shop in shoplist:
        total += sum(shop)

    return total

shoptotal([[2,3], [3,4,5], [1,2]])

# Nested loops

def shoptotal(shoplist):
    """ Takes a list of lists of numbers as input and returns
    the sum of all of those numbers. """

    total = 0

    for shop in shoplist:
        for number in shop:
            total += number

    return total

shoptotal([[2,3], [3,4,5], [1,2]])

# While loops

def fpot(n):
    """ Takes a number n as input and returns the smallest power
    of 2 that is greater than or equal to n."""

    power = 1 # 1 is the smallest power of 2
    while power < n:
        power = power * 2

    return power

fpot(100)

# For or While: for loop is preferable when we know in advance 
# how many times to loop whereas a while loop is ideal when we don't know in advance

def find(DNA, pattern):
    """ Takes a DNA string and a pattern string as input and
    returns the list of starting indices where the pattern
    string is found in the DNA string. """

    indexlist = []

    for i in range(0, len(DNA)):
        if DNA[i:i+len(pattern)] == pattern: #  Python is clever enough to realise that the ending index is not correct, and it will reduce the index to len(DNA) automatically
            indexlist.append(i)

    return indexlist

find('CTAGACTAGCC', 'TAG')

# a more complicate findcoding

def findcoding(DNA):
    """ Takes a DNA strings as input and finds the first coding
    region in that string."""

    for i in range(0,len(DNA)):
        # if the next 3 symbols are a start codon
        if DNA[i:i+3] == "ATG":
            # The starting position of the next codon
            j = i + 3

            while DNA[j:j+3] != "TAG" and \
                  DNA[j:j+3] != "TAA" and \
                  DNA[j:j+3] != "TGA":
                
           # while not DNA[j:j+3] in ["TAG", "TAA", "TGA"]:
                        
                # move three positions to the next codon
                j += 3

            # return the coding slice
            return DNA[i:j+3]
    
findcoding('GGATGAAATAGCC')

# two dimensional array

creatures = [ [0, 0, 0, 0], [1, 1, 0, 1], [0, 0, 0, 1] ]

# get rows and cols by len(creatures) and len(creatures[0])

print(len(creatures), len(creatures[0]))

# exchange 0 and 1 inside an 2d array

def change(array):
    """ Takes a list representing a 2D array as input and
    returns a list representing the array in which 0's are
    changed to 1's and 1's are changed to 0's. """

    rows = len(array)
    columns = len(array[0])

    for row in range(rows):
        for column in range(columns):
            
            # using if-else way
            if array[row][column] == 0:
                array[row][column] = 1
            else:
                array[row][column] = 0
                
            # another simpler way
            #array[row][column] = 1 - array[row][column]

    return array # return statement can be omitted as 2d array passed inside will be changed globally

newcreatures = change(creatures)

print(newcreatures)
print(creatures)

# what if we don't want to change the original array passed inside
# need to manually create another array and set its value

def change(input):
    """ Takes a list representing a 2D array as input and
    returns a new list representing the array in which 0's
    are changed to 1's and 1's are changed to 0's. """

    output = [] # our output array is initially empty
    rows = len(input)
    columns = len(input[0])

    for row in range(rows):
        newrow = [] # for each row in the input array
                    # we create a new row in the output array
        for column in range(columns):
            # For each item in the current row
            # add the "opposite" item in the new row
            newrow.append(1 - input[row][column])

        output.append(newrow) # add this new row to output

    return output

newcreatures = change(creatures)
print(newcreatures)
print(creatures)

# do not index an empty list

def change(input):
    """ Takes a list representing a 2D array as input and
    returns a list representing the array in which 0's are
    changed to 1's and 1's are changed to 0's. However, the
    code shown below does not work! """

    output = [] # our output array is initially empty
    rows = len(input)
    columns = len(input[0])

    for row in range(rows):
        for column in range(columns):
            # For each item in the current row
            # add the "opposite" item in the new row
            output[row][column] = 1 - input[row][column]

    return output

newcreatures = change(creatures)

# print a list

def printExample1():

    mylist = [1, 2, 3, 4, 5]

    for item in mylist:
        print(item)

    return

printExample1()

# print a list, without starting from a new line

def printExample2():

    mylist = [1, 2, 3, 4, 5]

    for item in mylist:
        print(item, end=" ")
       # print(str(item) + ":", end=" ") 

    return

printExample2()

# simple animation 

import time
from IPython.display import clear_output

# Set the number of seconds that have passed to zero
sec = 0

while True: # Repeat forever
    # This method of clearing the screen is for the IDLE
    # environment
    print("\n" * 1)

    # Show the number of seconds that have passed
    print(sec)
    if sec % 10 == 0:
        clear_output() # clear_output for notebook

    # Wait for 1 second
    time.sleep(1)

    # Update the number of seconds that have passed
    sec += 1

# basic dict

cantonese = {}
cantonese["thanks"] = "m goi"
cantonese["hello"] = "lei ho"

cantonese["hello"]

cantonese["goodbye"]

cantonese

# another way
cantonese = {'hello': 'lei ho', 'thanks': 'm goi'}
cantonese.keys()

# ask if there is a value associated with a given key
print("thanks" in cantonese, "cake" in cantonese)

from random import *

def play():
    """ This is a guessing game! Try to guess the computer's
    number which is an integer between 1 and 99. """

    print("Welcome!")

    # choice is from random package
    secret = choice(range(1, 100))
    numGuesses = 0
    userGuess = 0

    while userGuess != secret:

        userGuess = input("Enter your guess: ")
        userGuess = int(userGuess)
        numGuesses += 1

        if userGuess == secret:
            print("You got it in", numGuesses, "guesses!")
        elif userGuess > secret:
            print("Too high")
        else:
            print("Too low")

    print("Thanks for playing")
    
play()

# try-except-else for error handling
while True:
    try:
        ageString = input("What is your age? ")
        ageNum = int(ageString)
    except ValueError:
        print("You entered something that is not an integer.")
        print("Try again.")
    else:
        print("Thank you!")
        break

# more exception types
def find_ratio():
    while True:
        try:
            numerator = input("Enter a numerator: ")
            denominator = input("Enter a denominator: ")
            ratio = int(numerator)/int(denominator)
        except ValueError:
            print("You entered something other than a number")
            print("for the numerator or denominator. Try again.")
        except ZeroDivisionError:
            print("You entered zero for the denominator! Try again.")
        else:
            return ratio
    
find_ratio()

# write to and read from a file

def writeString():
    """ This function asks the user for a string and a file
    name and then makes a new file and stores that string in
    the file. """

    mystring = input("Enter a string that you want to save: ")
    filename = input("Enter a name of a file for writing: ")
    myfile = open(filename, "w") # open file for writing
    myfile.write(mystring) # write the string
    print('finish writing')
    myfile.close() # close the file

def readString():
    """ This function asks the user for a file name and then
    reads the contents of that file and returns it. """

    filename = input("Enter a name of a file for reading: ")
    myfile = open(filename, "r") # open file for reading
    mystring = myfile.read() # read contents into mystring
    myfile.close() # close file

    return mystring # return the string

writeString()
readString()

# catch exception if filename is wrong for reading

def readString():
    """ This function asks the user for a file name and then
    reads the contents of that file and returns it. """

    try:
        filename = input("Enter a name of a file: ")
        myfile = open(filename, "r")
    except IOError:
        print("There is no file with that name.")
    else:
        mystring = myfile.read()
        myfile.close()
        return mystring
    
readString()

# write multiple lines to a file

def writeMultipleStrings():
    """ This function asks the user for input strings and writes
    these strings to a file until an empty string is entered """

    filename = input("Enter a name of a file: ")
    myfile = open(filename, "w")
    mystring = input("Enter a string: ")

    while mystring != "":
        myfile.write(mystring + "\n")
        mystring = input("Enter a string: ")

    myfile.close()
    
writeMultipleStrings()

# read lines from a file

def readMultipleStrings():
    """ This function asks the user for a file name and reads
    the string in that file into a list. """

    try:
        filename = input("Enter a name of a file: ")
        myfile = open(filename, "r")
    except IOError:
        print("There is no file with that name.")
    else:
        mylist = myfile.readlines()
        myfile.close()
        return mylist

readMultipleStrings()

# scope concept revised

def firstfunc(x):
    print("The value of x in firstfunc(x) is: " + str(x))
    answer = secondfunc(x + 5) + x
    print("The value of x in firstfunc(x) is: " + str(x))
    return answer

def secondfunc(x):
    print("The value of x in secondfunc(x) is: " + str(x))
    x = 1
    print("The value of x in secondfunc(x) is: " + str(x))
    return x + 10

firstfunc(10)

# simple recursion example

def recursivefunc(x):
    print("The value of x in recursivefunc(x) is: " + str(x))
    if x < 20:
        answer = recursivefunc(x + 5) + x
    else:
        answer = x
    print("The value of x in recursivefunc(x) is: " + str(x))
    return answer

recursivefunc(10)

# classical example of factorial function

def factorial(n):
    """ Recursive function for computing factorial of n. """
    if n == 1:
        return 1
    else:
        result = n * factorial(n-1)
        return result
    
factorial(5)

# load turtle graphics module

from turtle import *

# draw a square
def square(length):
    """ Draws a square with the given side length """

    for i in range(4):
        forward(length)
        right(90)

reset()
square(100)

reset()
pencolor("purple") # turtle changes to purple pen
speed(10)          # set speed

# Draw a spiral structure from the center of the window
# outwards using a for loop
for i in range(0, 400, 2):
    forward(i)
    right(89)

# Draw another spiral structure from the outside of the window
# towards the center of the window using another for loop
for i in range(401, 0, -2):
    forward(i)
    right(89)

# draw polygons using recursion

def poly(length, angle, sides):
    if sides == 0:
        return
    else:
        forward(length)
        right(angle)
        poly(length, angle, sides-1)
        
reset()
poly(100, 40, 5)

# class example

import datetime # Needed by get_age() when it calculates the age

class Person:
    def __init__(self, name, date_of_birth, money, description):
        '''
        The constructor of the Person class which initializes
        the attributes of the class
        '''

        # Initialize the attribute "name"
        self.name = name
        # Initialize the attribute "date_of_birth"
        self.date_of_birth = date_of_birth
        # Initialize the attribute "money"
        self.money = money
        # Initialize the attribute "description"
        self.description = description

    def give_money(self, amount, targetPerson):
        '''
        Give money from this person object to the target person
        '''

        # Decrease the attribute "money" of this object
        self.money = self.money - amount

        # Then increase the money of the target instance
        # with the same amount
        targetPerson.money = targetPerson.money + amount

    def get_age(self):
        '''
        Get the age of this person object
        '''

        # Get today's date
        today = datetime.date.today()

        # Split the day, month and year from the
        # date_of_birth attribute and store them
        # into d, m and y variables
        [d,m,y] = self.date_of_birth.split("/")

        # Return the age
        return today.year - int(y)
    

kitty = Person("Hello Kitty", "13/12/1984", 10000, \
"Very energetic and loves to play outdoors")

mary = Person("Mary White", "28/11/1960", 50000, \
"Very kind and loving, and loves to cook")

george = Person("George White", "15/10/1957", 100000, \
"Hardworking and dependable, but has a good sense of humor")

mimi = Person("Mimi White", "13/12/1984", 5000, \
"Kitty's twin sister. She wears a ribbon on her right ear")

print(george.get_age(), mary.money)
mary.give_money(500, kitty)
print(mary.money, kitty.money)


if (kitty.money > mary.money):
    print(kitty.name + " is richer.")
elif (mary.money > kitty.money):
    print(mary.name + " is richer.")
else:
    print("They have same amount of money")
    
if (kitty.get_age() > mary.get_age()):
    print(kitty.name + " is older.")
elif (mary.get_age() > kitty.get_age()):
    print(mary.name + " is older.")
else:
    print("They have same age.")

# review question
john = Person("John", "15/6/1984", 1000, "Rich man")
paul = Person("Paul", "4/8/1974", 100, "Poor man")
mary = Person("Mary", "19/3/1992", 2000, "Young lady")

if mary.get_age() < john.get_age():
    mary.give_money(1000, john)
    
if mary.money > john.money:
    mary.give_money(500, paul)
else:
    john.give_money(500, paul)
    
print(mary.money, paul.money, john.money)