Custom Query (121 matches)

Reported by Scott David Daniels <Scott.Daniels@…>, 7 years ago.

Trying to import YAML fails in Python 2.5. Even simple patches fail, because the root cause is that NaNs and INFs cannot be marshalled/unmarshalled. Marshalling is used to save and restore compiled python modules, so a tested module can work initially, but later fail to load (when not from source).

When handling INFs and NaNs, you need to be careful. 1e300000 is not a safe way to represent infinity, and fails to pickle/unpickle safely from manifest constants. Different C runtimes represent the text for INFs and NaNs differently. Since Python 2.5 folds constants, a simple expression won't solve the problem.

The following changes should allow yaml to work on python 2.5a2 on Win2000 (and I think for 64-bit machines as well):

=============== constructor.py: ===============

*** 231,239 ****
          else:
              return sign*int(value)

-     inf_value = 1e300000
-     nan_value = inf_value/inf_value
-
      def construct_yaml_float(self, node):
          value = str(self.construct_scalar(node))
          value = value.replace('_', '')
--- 231,236 ----
***************
***************
*** 242,251 ****
              sign = -1
          if value[0] in '+-':
              value = value[1:]
!         if value.lower() == '.inf':
!             return sign*self.inf_value
!         elif value.lower() == '.nan':
!             return self.nan_value
          elif ':' in value:
              digits = [float(part) for part in value.split(':')]
              digits.reverse()
--- 239,253 ----
              sign = -1
          if value[0] in '+-':
              value = value[1:]
!         if value.lower() in ('.inf', '.nan'):
!             big = 1e300
!             bigger = big * big
!             while bigger > big and bigger == bigger:
!                 big = bigger
!                 bigger = big * big
!             if value.lower() == '.nan':
!                 return bigger / bigger
!             return sign * bigger
          elif ':' in value:
              digits = [float(part) for part in value.split(':')]
              digits.reverse()

=============== representer.py: ===============

*** 192,200 ****
      def represent_long(self, data):
          return self.represent_scalar(u'tag:yaml.org,2002:int', unicode(data))

!     repr_pos_inf = repr(1e300000)
!     repr_neg_inf = repr(-1e300000)
!     repr_nan = repr(1e300000/1e300000)

      def represent_float(self, data):
          repr_data = repr(data)
--- 192,206 ----
      def represent_long(self, data):
          return self.represent_scalar(u'tag:yaml.org,2002:int', unicode(data))

!     big = 1e300
!     bigger = big * big
!     while bigger > big and bigger == bigger:
!         big = bigger
!         bigger = big * big
!     repr_pos_inf = repr(bigger)
!     repr_neg_inf = repr(-bigger)
!     repr_nan = repr(bigger / bigger)
!     del big, bigger

      def represent_float(self, data):
          repr_data = repr(data)

Reported by alex_(a)_alexmole_(o)_co_(o)_uk, 7 years ago.

yaml.load( 'foo: -3.1' ) returns {'foo': 3.10000}

The same technique preserves the sign of integers though, so I presume it must be a bug rather than a yaml feature.

Reported by apopheniac.reply.pyyaml@…, 7 years ago.

If a string contains a space followed by a single quote character, PyYaml?'s emitter fails to duplicate the single quote. The resulting YAML output yields a parse error:

>>> map = {'key': " 'single quoted text'"}
>>> yaml.dump(map)
"{key: ' 'single quoted text'''}\n"
>>> yaml.load(yaml.dump(map))
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/home/apopheniac/lib/python/yaml/__init__.py", line 61, in load
    return loader.get_data()
  File "/home/apopheniac/lib/python/yaml/constructor.py", line 41, in get_data
    return self.construct_document(self.get_node())
  File "/home/apopheniac/lib/python/yaml/composer.py", line 23, in get_node
    return self.compose_document()
  File "/home/apopheniac/lib/python/yaml/composer.py", line 40, in compose_document
    node = self.compose_node(None, None)
  File "/home/apopheniac/lib/python/yaml/composer.py", line 69, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/home/apopheniac/lib/python/yaml/composer.py", line 112, in compose_mapping_node
    while not self.check_event(MappingEndEvent):
  File "/home/apopheniac/lib/python/yaml/parser.py", line 78, in check_event
    self.current_event = self.event_generator.next()
  File "/home/apopheniac/lib/python/yaml/parser.py", line 129, in parse_stream
    for event in self.parse_block_node():
  File "/home/apopheniac/lib/python/yaml/parser.py", line 323, in parse_node
    for event in collection_events:
  File "/home/apopheniac/lib/python/yaml/parser.py", line 472, in parse_flow_mapping
    "expected ',' or '}', but got %r" % token.id, token.start_mark)
yaml.parser.ParserError: while scanning a flow mapping
  in "<string>", line 1, column 1:
    {key: ' 'single quoted text'''}
    ^
expected ',' or '}', but got '<scalar>'
  in "<string>", line 1, column 10:
    {key: ' 'single quoted text'''}
             ^

If each single quote is preceded by a non-space character, then the error disappears:

>>> map = {"key": " foo'single quoted text'"}
>>> yaml.dump(map)
"{key: ' foo''single quoted text'''}\n"
>>> yaml.load(yaml.dump(map))
{'key': " foo'single quoted text'"}

The error seems to lie in the write_single_quoted function of module emitter.py. I've only encountered this problem with scalars represented in single quoted style.