jsno 1.0.3

Convert Python data to and from json-compatible data structures

jsno

Convert Python data to and from json-compatible data structures

Example

First, let's define a custom dataclass to keep track of domain data:

@dataclass
class DomainRecord:
    domain: str
    ips: list[str]
    enabled_at: date | None = None

Then, let's make a couple of such records:

domains = [
    DomainRecord(
        domain="example.com",
        ips=["93.184.216.34"],
        enabled_at=date(1992, 1, 1)
    ),
    DomainRecord(
        domain="another.example.com",
        ips=[]
    )
]

With jsno, these can be turned into JSON and stored in a local file:

jsonized = jsno.dumps(domains, indent=4)
pathlib.Path('domains.json').write_text(jsonized)

The file will look like this:

[
    {
        "domain": "example.com",
        "ips": ["93.184.216.34"],
        "enabled_at": "1992-01-01"
    },
    {
        "domain": "another.example.com",
        "ips": []
    }
]

To read and use the domains later:

jsonized = pathlib.Path('domains.json').read_text()
domains = jsno.loads(jsonized, as_type=list[DomainRecord])

assert domains[0].enabled_at.year == 1992

Native JSON types

The following types are native JSON types, and they are mapped to themselves when jsonifying and unjsonifying:

• str
• bool
• int
• float
• NoneType (None maps to JSON's null)
• list (JSON array)
• dict (JSON object)

Abstract base classes

The operations are also defined to the following abstract base classes, so any type implementing them can be jsnoified and unjsonified:

• Sequence (maps to list)
• Mapping (maps to dict)
• Set (maps to list)
• ByteString (maps to base64 encoded string)

Union types

Union types (typing.Union and T | U) are supported. However, when unjsonising union types, it's important that the JSON representations of two different types do not overlap.

Dataclasses

Dataclasses are supported. They get converted to JSON objects. The name of the class is not included in the result, unless the dataclass is a member of a variant family.

Other standard Python types

• tuples
• ranges
• enums
• date and datetime objects (converted to ISO-formatted strings)
• decimals (converted to JSON strings)
• pathlib.Path
• zoneinfo.ZoneInfo
• Literal (only int and str literals)