Implement the Dataset class

This is a review of the topics discussed that the Dataset class attributes must be:

Data: for version 1.0, use Pandas, subsequent versions will include streaming capabilities
Attached attributes: attributes at dataset level (simple dictionary at the moment, will be changed later)
Relationship to Schema class or URN

@sosna and @stratosn proposed the following code, which was accepted by everyone and will be implemented after 1.0, as some changes in parsers and writers are required.

from dataclasses import dataclass
from datetime import datetime
from typing import Any, Generator, Optional, Sequence, Union

from pysdmx.model import MetadataReport, DataProvider, Schema

@dataclass
class _Component:
    id: str
    value: Any

@dataclass
class Dimension(_Component):
    pass

@dataclass
class DataAttribute(_Component):
    pass

@dataclass
class Measure(_Component):
    pass

@dataclass
class _Package:
    key: str  # Full key (cf. MEDAL) A.F.G.M.*
    dimensions: Sequence[Dimension]
    attributes: Optional[Sequence[DataAttribute]]
    name: Optional[str]
    metadata: Optional[Sequence[MetadataReport, str]]

@dataclass
class Observation(_Package):
    measures: Sequence[Measure]

@dataclass
class _ObsPackage(_Package):
    observations: Generator[Observation]
    obs_count: Optional[int]
    start_period: Optional[str]
    end_period: Optional[str]
    last_updated: Optional[datetime]

@dataclass
class Series(_ObsPackage):
    pass

@dataclass
class Group(_Package):
    pass

@dataclass
class Dataset(_ObsPackage):
    packages: Generator[Union[Group, Series, Observation]]
    provider: Optional[DataProvider]
    structure: Union[Schema, str]  # Schema or the SDMX URN of the structure

    @property
    def groups(self):  # A view on the packages of type Group
        return (p for p in self.packages if isinstance(p, Group))

    @property
    def series(self):  # A view on the packages of type Series
        return (p for p in self.packages if isinstance(p, Series))

@dataclass
class PandasDataset(Dataset):
    def to_pandas():
        pass

bis-med-it / pysdmx

Implement the Dataset class #72