ValueError on "._" input

[Barro]

Following piece of code results in ValueError when given "._" input for PyYAML 3.12 to parse:

import sys
import yaml

try:
    list(yaml.safe_load_all(sys.stdin))
except yaml.YAMLError:
    pass

And is then run:

$ echo "._" | python validate-yaml.py
Traceback (most recent call last):
  File "validate-yaml.py", line 5, in <module>
    list(yaml.safe_load_all(sys.stdin))
  File "/home/jussi/.local/lib/python2.7/site-packages/yaml/__init__.py", line 83, in load_all
    yield loader.get_data()
  File "/home/jussi/.local/lib/python2.7/site-packages/yaml/constructor.py", line 33, in get_data
    return self.construct_document(self.get_node())
  File "/home/jussi/.local/lib/python2.7/site-packages/yaml/constructor.py", line 43, in construct_document
    data = self.construct_object(node)
  File "/home/jussi/.local/lib/python2.7/site-packages/yaml/constructor.py", line 88, in construct_object
    data = constructor(self, node)
  File "/home/jussi/.local/lib/python2.7/site-packages/yaml/constructor.py", line 282, in construct_yaml_float
    return sign*float(value)
ValueError: could not convert string to float: .

I would expect PyYAML only to return errors of type yaml.YAMLError, as documented, so that I can avoid catching arbitrary errors from that function, as that's generally considered bad style.

[perlpunk]

It seems the regular expression for floats used by pyyaml is not correct.
http://yaml.org/type/float.html
[-+]?([0-9][0-9_]*)?\.[0-9.]*([eE][-+][0-9]+)? (base 10)
Underscores are not allowed after the dot.
The ._ case could be fixed by disallowing only _ after the dot, but OTOH, according to the spec, underscores shouldn't be allowed there at all. Also, 1._ is recognized as a float by python, so currently it accepts 1._ but not ._.

Then again, the regex from the spec seems to be broken because it allows multiple dots.

Some tests are failing if I take out the _ after the dot.

Not sure what would be the best to do here.

[perlpunk]

I created #497

[tongxiaoge1001]

I created #497

Is this patch effective? I found that the communities were not merged. @perlpunk (26fd944)

[The-Compiler]

PyYAML 6.0 was released where this is fixed via #497, so I think this can be closed?

[ingydotnet]

@The-Compiler thanks. Closing.