Custom Query (121 matches)

Reported by rwb123@…, 7 years ago.

The following code produces bad yaml output, which subsequently dies in the yaml.load(). This is with pyyaml 3.0.3 on python 2.4.1.

import yaml

e = {"texas: '": 92.5}
yammy = yaml.dump(e)
print yammy
e2 = yaml.load(yammy)
print e2

The yaml output is:

$ python yamlbug2.py
{'texas: '': 92.5}

Traceback (most recent call last):
  File "yamlbug2.py", line 10, in ?
    e2 = yaml.load(yammy)
  File "/home/blahblah/dl/yaml/PyYAML-3.03/lib/yaml/__init__.py", line 61, in load
    return loader.get_data()
 ... etc.

Reported by tim.hochberg@…, 7 years ago.

If an object being passed to represet_data has a shorter lifespan than the representer, the results are unpredictable, but generally bad. In my case, I'm trying to represent a custom omap class. I register a representer like so:

def omap_representer(dumper, data):
    items = [[x, y] for (x, y) in data.iteritems()] 
    return dumper.represent_sequence(u'!omap', items)
    
yaml.add_representer(omap, omap_representer)

If I then dump something that contains multiple omaps, such as [one_omap,another_omap], the representer get's confused because it sees distinct objects that have the same id. Here's an actual example:

>>> a # Note that these are omaps not dictionaries, despite appearances.
[{1: 2, 2: 4}, {1: 99, 2: 88}]

>>> print yaml.dump(a)
- !omap
  - &id001 [1, 2]
  - &id002 [2, 4]
- !omap
  - *id001
  - *id002

Two approaches come to mind to fix this.

1. Hold onto a reference to the original object as well as to the serialized object in represented_objects. This is what I did as a temporary fix.
2. Do some sort of weak reference magic to track if an object dies and then delete it from represented_objects. This is more complicated and I'm not entirely sure it would work well. The upside is it's possibly more frugal with memory.

-tim

Reported by tim.hochberg@…, 7 years ago.

It is convenient to have YAML's output be consistent across runs. Some representers in PyYaml? do this already, but the dictionaries do not. I implemented a quick fix by replacing represent_dict with:

    def represent_dict(self, data):
        items = data.items()
        items.sort()
        return self.represent_mapping(u'tag:yaml.org,2002:map', items)

It might also be convenient to have custom sort orders as PyYaml? legacy does, but that's a bigger change.