loads_all produces an error when yaml loads classes serialization in file

[xancorreu@…]

Hi,

I have this code:

#!./bin/python3

import yaml

class ExcepcioTasca(Exception):

	def __init__(self, valor):
		self.value=valor

	def __str__(self):
		return repr(self.value)

class Tasca:

	def __init__(self, nombre):
		if isinstance(nombre, int):
			self.num = nombre
		else:
			self.num = None
			raise ExcepcioTasca("S'ha passat un valor no enter com a nombre de la tasca de la instància {0}".format(repr(self)))

	def __str__(self):
		return str(self.num)


class Enregistrador:

	def afegeix(self, tasca, fitxer='./tasques.yaml', protocol='yaml'):
		if protocol=='yaml':
			try:
				with open(fitxer, mode='a', encoding='utf-8') as f:
					yaml.dump(tasca, f)
			except TypeError as e:
				print("No es pot enregistrar aquest tipus de dada: {0} és {1}".format(tasca, type(tasca)))
		else:
			print("Protocol no suportat. En futures versions, els protocols suportats poden ser XML, JSON, CSV, etc.")


def main():
	try:
		t = Tasca(3)
		print(t)
		t2 = Tasca(0)
		print(t2)
		e = Enregistrador()
		e.afegeix(t)
		e.afegeix(t2)
		e.afegeix(t)
		e.afegeix(lambda x:0)
		with open('./tasques.yaml', mode='r', encoding='utf-8') as f:
			for data in yaml.load_all(f):
				print(data)
	except ExcepcioTasca as e:
		print("Ha ocorregut una excepció: {0}".format(e.value))

if __name__=='__main__':
	main()

The file is called y.py

When I run y.py (python3), I receive:

$ ./y.py 
3
0
No es pot enregistrar aquest tipus de dada: <function <lambda> at 0xa29e82c> és <class 'function'>
3
Traceback (most recent call last):
  File "./y.py", line 57, in <module>
    main()
  File "./y.py", line 51, in main
    for data in yaml.load_all(f):
  File "/home/xan/proves/xitz/simple/virtual/lib/python3.2/site-packages/yaml/__init__.py", line 83, in load_all
    while loader.check_data():
  File "/home/xan/proves/xitz/simple/virtual/lib/python3.2/site-packages/yaml/constructor.py", line 26, in check_data
    return self.check_node()
  File "/home/xan/proves/xitz/simple/virtual/lib/python3.2/site-packages/yaml/composer.py", line 18, in check_node
    if self.check_event(StreamStartEvent):
  File "/home/xan/proves/xitz/simple/virtual/lib/python3.2/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/home/xan/proves/xitz/simple/virtual/lib/python3.2/site-packages/yaml/parser.py", line 174, in parse_document_start
    self.peek_token().start_mark)
yaml.parser.ParserError: expected '<document start>', but found '<tag>'
  in "./tasques.yaml", line 2, column 1


Why I receive that? If pyyaml was able to serialize my class Tasca, then it's logic that it were able to deserialize. I don't know reasons to fail, so I report bug.

Thanks in advance,
Xan.

PS: I run ubuntu with virtualenv. So I get the lastest version of pyyaml via pypi.