pyaml output stringified inexplicably in places about pretty-yaml HOT 1 CLOSED

It's happening because you're using "safe=True" there, which ensures that PyYAML's more robust serialization is used, and de-serialized data will be same as original, at the cost of some prettiness.

Reason why that one string is singled-out for escaping is simple - only 0.51 will be de-serialized as a number (0.51), while 0.5.1 and 0.7.1 will be interpreted as strings anyway (due to two dots in there), so no need for quotes there.

If you won't be passing safe=True, you should get desired output, but when de-serialized by any sane YAML parser, it will not match the original types, as mentioned.

Example:

% python3 -m pyaml <<< "{'y': ['0.5.1', '0.51', '0.7.1']}"
y:
  - 0.5.1
  - 0.51
  - 0.7.1

% python3 -c 'import yaml; print(yaml.safe_load("{y: [0.5.1, 0.51, 0.7.1]}"))'
{'y': ['0.5.1', 0.51, '0.7.1']}

Note missing quotes around 0.51 in the last output, indicating that it indeed was parsed as a float object instead of string.

It's an intended behavior that "unsafe" (default) serializer may produce such quirks (though hopefully not many), with human-readability preferred over correctness.
Same thing also mentioned in #20, I believe.

from pretty-yaml.