'''
One of robots is charged with a simple task: to join a sequence of strings
in one sentence to produce instructions on how to get around the ship.
But this robot is left-hander and has a tendency to joke around and confuse
its right handed friends.
You are given a sequence of strings. You should join these strings into
chunk of text where the initial strings are separated by commas. As a joke
on the right handed robots, you should replace all cases of the words "right"
with the word "left", even if it's a part of another word. All strings are
given in lowercase.
Input: A sequence of strings as a tuple of strings (unicode).
Output: The text as a string.
Precondition:
0 < len(phrases) < 42
'''
def change(word):
    return word.replace('right', 'left')

def left_join(phrases):
    """
        Join strings and replace "right" to "left"
    """
    response = ''.join([change(x)+',' for x in phrases])
    return response[:len(response)-1]

if __name__ == '__main__':
#These "asserts" using only for self-checking and not necessary for auto-testing
    assert left_join(("left", "right", "left", "stop")) == "left,left,left,stop"
    assert left_join(("bright aright", "ok")) == "bleft aleft,ok"
    assert left_join(("brightness wright",)) == "bleftness wleft"
    assert left_join(("enough", "jokes")) == "enough,jokes"
