# lecture 10.10.2023, repetition statements, also known as: loops
print("Welcome!")

# NEW FILE

# a simple for-loop: 10 cycles
# basically: we ask Python to run this line of
# code 10 times in a row
for x in range(10):
    # this is the line we ask Python to run 10 times in a row
    print(x)

# ANOTHER VERSION

# a simple for-loop: 10 cycles
# basically: we ask Python to run this line of
# code 10 times in a row
for x in range(10):
    # this is the line we ask Python to run 10 times in a row
    print(f"Number: {x}")

# NEw FILE

# usually we place the range limits
# into variables
start = 2017
end = 2023

# we can also define start and end
# of the range
for year in range(start, end):
    print(year)

# ANOTHER VERSION

# usually we place the range limits
# into variables
start = 2017
end = 2023

# we can also define start and end
# of the range
# third parameter is called step
# if you use 2, the loop skips in increments of 2
# instead of 1 (default step is 1)
for year in range(start, end, 2):
    print(year)

# NEW FILE
# you can try this in Python Tutor also
# to visualize the logic
# create an empty text variable
text = ""

# the idea is build the text-variable
# from pieces in a loop
for year in range(2017, 2024):
    text = text + str(year) + "-"

# let's remove the extra dash from the end
# this substring means: take everything from
# beginning until second last character
text = text[:-1]
print(text)

# NEW FILE

print("Start!")

# a simple for + if/else
# each cycle checks if the number is even or odd
for x in range(10):
    if x % 2 == 0:
        print("Even!")
    else:
        print("Odd!")

print("App ended.")

# NEW FILE

# counter variable, initialize to 1
# can also be 0
counter = 1

# while-loop is similar to if-statement, it has a condition
# so while the counter variable is less or equal to 10
# => keep running this code
while counter <= 10:
    print(counter)

    # always increment (add 1) to counter
    # in the end of each cycle
    # otherwise we get an infinite loop
    # because counter will always be under 10
    counter = counter + 1

# NEW FILE

# create a helper variable that keeps track
# if our application should still be running
running = True

# our main loop, run the code as long as the user wants to
while running:
    print("App is running!")

    # ask user a number for this cycle of app
    number = input("Give a number:\n")
    number = int(number)

    # double the number and print it out
    total = number * 2
    print(f"Number doubled: {total}")
    print()

    # ask user if they still want to continue with the app
    choice = input("Would you like to continue? (y/n)?\n")

    # if users inputs "n" => exit the app
    if choice.lower() == "n":
        running = False

# this is run afterwards as the final code line
# when the while loop above ends (user inputs "n")
print("Thank you for using our application!")

# NEW FILE

# nesting loops

print("Start!")

for x in range(3):
    print(f"MAIN LOOP, x = {x}")

    # whatever is inside this main loop
    # is run 3 times (range(3))
    # including nested loops
    # so this loop is also run 3 times
    for y in range(5):
        print(f"\tNested for-loop: y = {y}")


print("End app!")

# A MORE PRACTICAL VERSION OF THE ABOVE

print("Today's sales report:")

# we could also have a more complex nesting
# for example:
# department -> order -> product

# first, let's loop all our orders
for order in range(3):
    print(f"Processing order: {order}")

    # each order has 5 products
    # => loop through all the products in
    # this cycle's product
    for product in range(5):
        print(f"\tProcessing order {order}, product {product}!")

print("All ready.")

# ANOTHER EXAMPLE

print("Start app!")

# 5 persons in line
for person in range(5):
    # new person in turn
    print(f"Person {person + 1} turn!")

    # it's this person's turn to say numbers 1-4
    for number in range(4):
        print(f"Person {person + 1} says number: {number + 1}!")


print()
print("Everyone has spoken!")

# NEW FILE

print("Start!")

for x in range(5):
    # if x == 3 => stop this for-loop
    # and continue after the for-loop
    if x == 3:
        break

    print(x)

print("End.")

# NEW FILE

print("Start!")

for x in range(5):
    # if x == 3 => skip this cycle
    # and continue where x = 4
    if x == 3:
        continue

    print(x)

print("End.")

# NEW FILE

total = 0

# ask user 10 times a number
# add the number to the total -variable
for x in range(10):
    number = int(input("Give number:\n"))
    total = total + number

# what is the sum in them
print(total)

# NEW FILE

# how many cycles we want to ask the number
# any integer works, even random integers (as long as it's an integer)
cycles = int(input("How many numbers to ask?\n"))
total = 0

# run the for-loop as many times as user wanted
# and accumulate the total -variable
for x in range(cycles):
    number = int(input("Give number:\n"))
    total = total + number

print(total)

# NEW FILE

# interest calculator

# compound interest, with loops instead of mathematical equation
# yearly interest = 7%
# add 2000€ in the beginning of each year

start_money = 15000
yearly_money = 2000

# interest of 7%, use 1.07 for easier multiplication
interest = 1.07

# the goal is to find out the amount of new money after 10 years of saving

total = start_money

# use Python to calculate interest
# for our money 10 years in a row
for year in range(10):
    # in the beginning of each year, add 2000€ more
    total = total + yearly_money

    # calculate interest
    total = total * interest

# total money in the end
total = round(total, 2)
print(f"Money after 10 years of saving: {total} €")

# new money in the end => how much profit we had
profit = total - start_money - (10 * yearly_money)
print(f"After 10 years, our profit is = {profit} €")

# NEW VERSION

# VERSION 2: Interest calculator / compound interest
# how many years does it take for us to reach a certain profit

start_money = 15000
yearly_money = 2000

# what is our target savings
target_profit = 150000

# 7% interest per each year
interest = 1.07

# helper variables for the loop to keep track of current situation
total = start_money
current_profit = 0

# for-loop for years 1-30
for year in range(1, 31):
    # add the yearly money
    total = total + yearly_money

    # add interest
    total = total * interest

    # update how much profit we have earned so far
    current_profit = total - start_money - (year * yearly_money)

    # check if we have met our goal yet
    if current_profit >= target_profit:
        print(f"We met our goal in the year: {year}")
        # since we already know the year, no point continuing
        # the loop => break
        break

# if we didn't get to the target profit
# print an informing message for the user
if current_profit < target_profit:
    print("This goal cannot be met within this time limit and starting investment.")

# ANOTHER EXAMPLE, CLASSIC: FIBONACCI

# Fibonacci sequence: every number is the sum of two previous numbers
# first 9 numbers are: 0, 1, 1, 2, 3, 5, 8, 13, 21

# OUR GOAL: ask user a number: which Fibonacci number do they
# want to see, and count the value with a for-loop

# examples:
# if user inputs 5 = 1 + 2 = 3
# if user inputs 6 = 2 + 3 = 5
# if user inputs 7 = 3 + 5 = 8
# if user inputs 8 = 5 + 8 = 13
# x. number is old number + new number = fibonacci number

# helper variables to keep track of old and new number
old_number = 0
new_number = 1

# initialize fibonacci number to be 1 in the beginning
fibonacci = 1


choice = input("Which Fibonacci number would you like to see?\n")
choice = int(choice) - 2
print()

# for-loop that counts the Fibonacci number
# until the choice-variable dictates

for number in range(choice):
    print("New cycle!")
    # calculate the current value
    fibonacci = old_number + new_number

    print(f"Fibonacci is now: {old_number} + {new_number} = {fibonacci}")

    # update the old number
    old_number = new_number

    # update the new number to be whatever fibonacci is now
    new_number = fibonacci

    print(f"After this cycle: old_number = {old_number}, new number = {new_number}")
    print()

print()
print(f"Fibonacci number = {fibonacci}")