====== Computer Lab 14, comprehensive exercises ======

  * 1. Implement the following function:
<code python>
def abs_2(x):
    """Return an absolute value of x-2, i.e., y=|x-2|.
 
    :param x: int, float. 
    :return: int, float. The absolute value of x-2.
    >>> abs_2(0)
    2
    """
</code>

  * 2. Implement the following function (pure function!). You can re-use ''abs_2()''.
<code python>
def abs_2_list(lst):
    """Return a list of absolute values of x-2, where x's are elements of lst.
 
    :param lst: list of ints/floats. 
    :return: list of ints/floats.
    >>> abs_2_list([0, 2, 4])
    [2, 0, 2]
    """
</code>

  * 3. Consider a file with the following content:
//number_file.txt//
<code>
1,2,3,4
90,23,78,0,23,23
9,8,7,-5,-12,0,12,12,12
0,-8
3,3,3,3
</code>
Implement a function which outputs a list of sums of numbers from each line of the file. Return None if the file does not exist.
<code python>
def sum_file(file_name):
    """Return a list of row sums.
 
    :param file_name: Path to a text file. 
    :return: list of ints/floats.
    >>> sum_file("number_file.txt")
    [10, 237, 43, -8, 12]
    """
</code>

  * 4. Implement four methods (%%__init__%%, %%__str__%%, %%__eq__%%, %%__add__%%) for the following class according to their tests. 
<code python>
import unittest

class ColorRGB:
    """Represents a color in the R (red), G (green), B (blue) format."""
    
class TestColorRGB(unittest.TestCase):
    """Test ColorRGB methods"""

    def test_init(self):
        """Test that the initializer method __init__ takes 3 parameters"""
        ColorRGB(255, 0, 255)

    def test_str(self):
        """Test string conversion"""
        self.assertEqual("ColorRGB(0,127,127)", str(ColorRGB(0, 127, 127)))

    def test_eq(self):
        """Test deep equality for two ColorRGB instances"""
        self.assertEqual(ColorRGB(0,30,255), ColorRGB(0,30,255))

    def test_add(self):
        """Test the plus operator between two instances of the ColorRGB class"""
        color1 = ColorRGB(30, 100, 255)
        color2 = ColorRGB(0, 255, 30)
        self.assertEqual(ColorRGB(30, 255, 255), color1 + color2)
        self.assertEqual(ColorRGB(30, 100, 255), color1)
        self.assertEqual(ColorRGB(0, 255, 30), color2)


if __name__ == "__main__":
    # Execute all unit tests
    unittest.main()
</code>

  * 5. Implement the following function:
<code python>
def random_integers(length, lower_bound, upper_bound):
    """Build a list of randomly chosen integers.

    :param length: Length of the resulting list
    :param lower_bound: Lower bound of each random integer (INCLUDED)
    :param upper_bound: Upper bound of each random integer (INCLUDED)
    :return: List of random integers
    """
</code>

  * 6. Create the following lists using list comprehension:
<code python>
# 1.
fruits = ["apple", "banana", "pear", "kiwi", "strawberry", "lime", "lemon", "orange"]
# only words of even number of letters, transform them to uppercase

# 2.
# List of |x-2| where x's are all integers in the closed interval [-10, 10].

</code>