object has no attribute 'ecrire'

[fulgar36 at gmail.com]

Hello,
I wrote this code (it was on a book)

class TableauNoir:
	def __init__(self):
		self.surface=""
	def ecrire(self, message_a_ecrire):
		if self.surface != "": 
			self.surface += "\n"
		self.surface+=message_a_ecrire
it does not run on the shell and tells (object TableauNoir has no attribute 'ecrire'
could you tell me why it does not work. in the book ecrire should be a method from the class not an attribute
thanks