Hiss Byte Notation

Library to make it easy to use python literal syntax as a data format

Have you seen people try to print a dict and then use the JSON library to parse the output? This library is some helper function for that scenario. It is a small wrapper around ast.literal_eval and will have a API similar to other serializer/deserializers such as json, pickle, pyyaml, etc.

Safety

ast.literal_eval is safer than eval but the python docs still imply that there are malicious payloads. I'm not sure if they are the same problems that could affect json or other formats.

Usage

import hissbytenotation as hbn

data = {
    "mammal": "cat",
    "reptile": ["snake", "lizard"],
    "version": 1
}
data_as_string = hbn.dumps(data)

rehydrated = hbn.loads(data_as_string)
print(rehydrated)
# {'mammal': 'cat', 'reptile': ['snake', 'lizard'], 'version': 1}

How it works

Serialization is done by calling repr, checking if ast.literal_eval can read it. Repr can be called on more data structures than ast.literal_eval can handle.

Because ast.literal_eval is so slow, there are other options for deserialization:

• default: ast.literal_eval with validation enabled. Very slow, very safe.
• eval. Slow, only for trusted data.
• exec. Slow, only for trusted data.
• import. Two times faster than exec, only for trusted data.

Serialization and deserialization times for 10,000 dumps/loads

Pickle:  0.89 seconds
JSON: 2.00 seconds
HBN (no validation): 20.80 seconds
HBN (validation): 40.57 seconds
HBN (unsafe): 15.95 seconds
HBN (exec): 18.08 seconds
HBN (by import): 12.26 seconds

Prior art

• literal-python-to-pickle A faster replacement for ast.literal_eval and corresponding question on stackoverflow.

• You could just call repr and ast.literal_eval directly.

Possibly astor which serializes to a string representation of the AST, which looks nothing like the source code, nor json.