📑 Max Product of Three

📑 Task

1) Find a mistake in the process of recursion the function
for calculating the maximum product of three numbers in the list
2) Suggest a possible decision to build a recursive function

📑 Answer

1) Incorrect recursion logic: if the list becomes longer by one element,
then all the indices of the elements that give the maximum product
could be changed, not only one index
2)

📑 Referring to the Same Object

📑 Task

1) Will the result of printing the values for the functions f1 and f2
be the same in all cases?
2) Print out the values of the function f2 at x = 1, 2, 3 so
that the result will be the same for all x

📑 Answer

1) When printed in a loop, the functions' values will be equal
For f1 the default list-argument changes
(it was set when the function was defined)
For f2 the same list-variable changes
(it was set as a global variable)
When printed by the generator, the functions' values become different
f1 continues to expand the default list-argument
f2 begins to expand the empty list-variable again
2)

📑 Neuron Activations

📑 Task

1) Can you describe the goals of creating this type of objects?
2) Try to modify this class so that it becomes more
multifunctional and has several activation methods

📑 Answer

1) This Neuron class aims to provide a foundation for understanding how
individual neurons process input data and produce output in a neural network
2)

📑 Different Behavior of Functions

📑 Task

1) How will using this decorator affect the function?
2) Can you build your own decorator function that will affect the behavior
of user-defined or built-in functions depending on the arguments?

📑 Answer

1) This gives the function different behavior depending on the type of its argument
2)

📑 Countdown Timers

📑 Task

1) Explain the sequence of actions of this program
2) Can you suggest an alternative code for timing only in Python?

📑 Answer

1) This code renders the countdown timer in the output area
of the Jupyter notebook or IPython environment
It based on Javascript and HTML components, stored in Python strings
2)

import time
from datetime import datetime
def timer(maxiter=100):
    for i in range(maxiter):
        time.sleep(1)
        print(f"🕒 {(59 - datetime.now().second):0>2}", 
              flush=True, end='')
        print("\r", flush=True, end='')
timer()

📑 Memorization Decorators

📑 Task

1) What is the decorator used for in the second function definition?
2) Can you write your own decorator for the same goal?

import functools, time
def fibonacci1(n):
    if n < 2: return n
    return fibonacci1(n - 1) + fibonacci1(n - 2)
# a least-recently-used (LRU) cache eviction policy
@functools.lru_cache(maxsize=None)
def fibonacci2(n):
    if n < 2: return n
    return fibonacci2(n - 1) + fibonacci2(n - 2)
code_str = lambda f, n: f"""
start = time.time(); {f(n)}; stop = time.time() 
print(f'{f}: {{stop - start: e}}')"""
for f in [fibonacci1, fibonacci2]:
    exec(code_str(f, 30))

📑 Answer

1) The memoization provided by `functools.lru_cache` prevents redundant calculations
by storing previously computed Fibonacci numbers and
retrieving them from the cache when needed
2) The decorator with custom cache eviction policies and
different data structures for the cache

def cache(func):
    @functools.wraps(func)
    def wrapper_cache(*args, **kwargs):
        cache_key = args + tuple(kwargs.items())
        if cache_key not in wrapper_cache.cache:
            wrapper_cache.cache[cache_key] = func(*args, **kwargs)
        return wrapper_cache.cache[cache_key]
    wrapper_cache.cache = dict()
    return wrapper_cache
@cache
def fibonacci3(n):
    if n < 2: return n
    return fibonacci3(n - 1) + fibonacci3(n - 2)
for f in [fibonacci1, fibonacci2, fibonacci3]:
    exec(code_str(f, 30))

📑 Sets and Elements

📑 Task

1) What will be the result of running the program?
2) Suggest as many other ways as possible to add and remove this element from the set
How else can a mini- program check if there is an element in a given set?

📑 Answer

1) Outputs: {0, '♗', '♙', 1, 2, 3, '♕', '♔', 4, '♖', '♘'} ♘ and False
2)