03_solutions.py

# -*- coding: utf-8 -*-
"""03_solutions.py

Author -- Michael Widrich
Contact -- widrich@ml.jku.at
Date -- 01.10.2019

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The following copyright statement applies to all code within this file.

Copyright statement:
This material, no matter whether in printed or electronic form, may be used for
personal and non-commercial educational use only. Any reproduction of this
manuscript, no matter whether as a whole or in parts, no matter whether in
printed or in electronic form, requires explicit prior acceptance of the
authors.

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Example solutions for tasks in file 03_tasks.py.

"""

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# 03 Functions and Printing
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#
# Task 1
#

# Write a function that divides two numbers and returns the result. The
# numbers should be taken as keyword arguments with defaults of 1.0 for both
# values.

# Your code here #


def my_divide(numerator=1.0, divisor=1.0):
    return numerator / divisor


result = my_divide(5, 3)
print(result)


#
# Task 2
#

# Write a function that takes one argument that can be assumed to be a list.
# The function should add up the last two elements in the list, print the sum,
# and append it at the end of the list without any return value.

a = [1, 2, 3, 5]

# Your code here #


def my_funct(l):
    s = l[-2] + l[-1]
    l.append(s)
    
    
my_funct(a)
print(a)


#
# Task 3
#

# Write a function my_function() that takes an arbitrary number of positional
# arguments as input. You can assume these arguments are either strings or
# nested lists of strings.
# Create a flat (=not nested) list from these arguments that holds only the
# strings. Add 'image' to the beginning of each strings if the string ends
# with '.png' ('file1.png' -> 'imagefile1.png'), 'text' if the string ends
# with '.txt', and 'data' otherwise. You can use a recursive
# function to solve this task.
# Useful functions:
# 'string'.endswith('substring') to check if a string ends with a certain
# substring.
# isinstance(a, list) to check if variable "a" is of type list

# Example function call:
some_list = ['file2.txt', 'file3.txt']
some_nested_list = ['file4.png', 'file5.txt', ['file6.txt', 'file7.dat']]
# my_list = my_function('file0.txt', 'file1.png', some_list, some_nested_list)

# Your code here #


def my_function(*args):
    # First we create a new list
    result = []
    # Then we loop over the input arguments
    for arg in args:
        if isinstance(arg, str):
            # If the argument is a string, add the substrings at the beginning
            # and append it to our "result"-list
            if arg.endswith('.png'):
                result.append('image' + arg)
            elif arg.endswith('.txt'):
                result.append('text' + arg)
            else:
                result.append('data' + arg)
        elif isinstance(arg, list):
            # If the argument is a list, call the function again to process the
            # list recursively. It will return the processed list of strings
            # so we can just concatenate it with our "result"-list.
            arg_result = my_function(*arg)
            result += arg_result
    return result


#
# Task 4
#

# Write a function next_element(my_iterable) that returns an iterable that
# yields the next element in my_iterable.
# If the list is exhausted (i.e. if the last element has been reached), the
# next element should be the first list element.
# Write a loop that calls next_element() 25 times and prints the currently
# returned value of next_element().
# Example function call:
# next_element('abcdefg')

# Your code here #


def next_element(my_iterable):
    """Returns iterable that yields next element in my_iterable and start from beginning if my_iterable is exhausted"""
    i = 0
    while True:
        yield my_iterable[i]
        i += 1
        if i >= len(my_iterable):
            i = 0


# Alternative 1:
def next_element(my_iterable):
    """Returns iterable that yields next element in my_iterable and start from beginning if my_iterable is exhausted"""
    i = 0
    while True:
        yield my_iterable[i % len(my_iterable)]  # % is the modulo operator - it returns the remainder after a division
        i += 1


for i, element in enumerate(next_element('abcdefg')):
    print(f"element: {element}")
    if i >= 24:
        break


#
# Task 5
#

# Write a function next_element(my_iterable, max_iter) that returns an iterable
# that yields the next element in my_iterable.
# If the list is exhausted (i.e. if the last element has been reached), the
# next element should be the first list element. A maximum of max_iter elements
# shall be returned.
# Write a loop that calls next_element(my_iterable, max_iter) until max_iter is
# reached and prints the currently returned value of next_element().
# Example function call:
# next_element('abcdefg', max_iter=20)

# Your code here #


def next_element(my_iterable, max_iter):
    """Returns iterable that yields next element in my_iterable and start from beginning if my_iterable is exhausted"""
    i = 0
    for _ in range(max_iter):
        yield my_iterable[i]
        i += 1
        if i >= len(my_iterable):
            i = 0


# Alternative 1:
def next_element(my_iterable, max_iter):
    """Returns iterable that yields next element in my_iterable and start from beginning if my_iterable is exhausted"""
    i = 0
    j = 0
    while True:
        yield my_iterable[i]
        i += 1
        j += 1
        if i >= len(my_iterable):
            i = 0
        if j >= max_iter:
            break


# Alternative 2:
def next_element(my_iterable, max_iter):
    """Returns iterable that yields next element in my_iterable and start from beginning if my_iterable is exhausted"""
    for i in range(max_iter):
        yield my_iterable[i % len(my_iterable)]  # % is the modulo operator - it returns the remainder after a division


for element in next_element('abcdefg', max_iter=20):
    print(f"element: {element}")