useful commands

coroutine.py

from collections import namedtuple
def coroutine(func):
    def start(*args, **kwargs):
        cr = func(*args, **kwargs)
        next(cr)
        return cr 
    return start

# @coroutine
# def my_coroutine(a):
#     """Yield expression will yield every value sent to the coroutine
#     and assign that value to the variable on the left
#     Coroutines are consumers of data. Coroutines are just another concurrency model
#     Generators produce data for iteration
#     """
#     print(f"Started with {a}")
#     b = yield 
#     print(f"But continues with {b}")

@coroutine
def averager_with_result():
    Result = namedtuple("Result",["Count", "Average"])
    total = 0
    sum = 0
    average = None
    while True:
        value = yield average
        if value is None:
            break
        total += 1
        sum += value
        average = sum / total 
    return Result(total, average)

# averager = averager_with_result()

# averager.send(2)
# averager.send(4)
# averager.send(1)
# averager.send(5)
# averager.send(None)

decorators.py

    """Augmenting functions without modifications
    """

#Without Decorator

def adder(a,b):
    return a + b

## print(adder(2,3)) --> 5


#######
#######
#With Decorator
def decorat(func):
    def times_10(x,y):
        return func(x*10, y*10)
    return times_10

@decorat
def adder(a,b):
    return a + b

## print(adder(2,3)) --> 50 

memoized_fibonacci.py

def fibonacci(input_value):
    if input_value == 1:
        return 1
    elif input_value ==2:
        return 1
    else:
        return fibonacci_memo(input_value - 1) + fibonacci_memo(input_value - 2)

fibonacci_cache = {}

def fibonacci_memo(input_value):
    if input_value in fibonacci_cache:
        return fibonacci_cache[input_value]
    if input_value == 1:
        value = 1
    elif input_value == 2:
        value = 1
    elif input_value > 2:
        value = fibonacci_memo(input_value - 1) + fibonacci_memo(input_value - 2)
    fibonacci_cache[input_value] = value
    return value

pdf_encrypt.py

# pip install PyPDF2

from PyPDF2 import PdfFileWriter, PdfFileReader

def add_encryption(input_pdf, output_pdf, password):
    pdf_writer = PdfFileWriter()
    pdf_reader = PdfFileReader(input_pdf)

    for page in range(pdf_reader.getNumPages()):
        pdf_writer.addPage(pdf_reader.getPage(page))

    pdf_writer.encrypt(user_pwd=password, owner_pwd=None, 
                    use_128bit=True)

    with open(output_pdf, 'wb') as fh:
        pdf_writer.write(fh)

if __name__ == '__main__':
    add_encryption(input_pdf='merged.pdf',
                output_pdf='merged-encrypted.pdf',
                password='twofish')

recursive_factorial.py

def factorial(n):
    if (n<=1):
        return 1
    else:
        subSolution =factorial(n-1)
        solution = subSolution * n
        return solution

factorial(3)