ValueError: cannot switch from manual field specification to automatic field numbering

Question

The class:

class Book(object):
    def __init__(self, title, author):
        self.title = title
        self.author = author

    def get_entry(self):
              


        

Answer 1

return "{0} by {1} on {}".format(self.title, self.author, self.press)

that doesn't work. If you specify positions, you have to do it through the end:

return "{0} by {1} on {2}".format(self.title, self.author, self.press)

In your case, best is to leave python treat that automatically:

return "{} by {} on {}".format(self.title, self.author, self.press)