Could I have done this better?

Afternoon. I have completed The Hard Way to Python all the way up to classes but I decided before continuing that I should try to cement the skills I have. But I'm already really struggling with the elementary tasks here (Using all the hints, looking up how things work). So, if I do come upon a solution I want to put it in the discuss section to see if any improvements could be made to it.

Here is my solution to "Right to left"

def left_join(phrases):

"""

    Join strings and replace "right" to "left"

"""

string = ','.join(phrases).replace('right', 'left')

return string