Dataclasses howto (code for the carbon.now.sh images)

dataclasses_howto.py

import json
from datetime import datetime
from datetime import date
from pydantic.dataclasses import dataclass
from dataclasses import asdict

@dataclass(frozen=True, order=True)
class Foo:                                      
    name: str 
    int_value: int
    float_value: float
    ts: datetime
    dt: date
        
@dataclass(frozen=True, order=True)
class Bar:                                      
    name: str 
    value: Foo
        
datetime_to_str = lambda v: v.isoformat() if isinstance(v, (datetime, date)) else None        

bar=Bar('bar', Foo('foo', 1, 1/3, datetime.now(), datetime.now().date()))

str_bar = json.dumps(asdict(bar), default=datetime_to_str)

bar_data = json.loads(str_bar)

print(Bar(**bar_data))

Bar(name='bar', value=Foo(name='foo', int_value=1, float_value=0.3333333333333333, ts=datetime.datetime(2022, 8, 13, 12, 38, 45, 46213), dt=datetime.date(2022, 8, 13)))
--------------
import json
from typing import Dict, List, Any, Tuple
from dataclasses import dataclass, asdict, field

@dataclass(frozen=True, order=True)
class Foo:                                      
    name: str 
    dict_value: Dict[int, Any] = field(hash=False)
    lst_value: List[str] = field(hash=False)
    tuple_value: Tuple[Any]
    ignored_lst_value: List[str] = field(compare=False, hash=False)
    
foo = Foo('foo', {1: 'a', 2: []}, ['b', 3], ('c', 4), [1,2,3])
--------------
import json
from datetime import datetime
from datetime import date
from dataclasses import dataclass, asdict

@dataclass(frozen=True, order=True)
class Foo:                                      
    name: str 
    int_value: int
    float_value: float
    ts: datetime
    dt: date
        
    @classmethod
    def from_data(cls, data):
        return Foo(
            name=data['name'],
            int_value=data['int_value'],
            float_value=data['float_value'],
            ts=datetime.fromisoformat(data['ts']),
            dt=datetime.fromisoformat(data['dt']).date()
        )
    
@dataclass(frozen=True, order=True)
class Bar:                                      
    name: str 
    value: Foo
        
    @classmethod
    def from_data(cls, data):
        return Bar(
            name=data['name'],
            value=Foo.from_data(data['value'])
        )
        
datetime_to_str = lambda v: v.isoformat() if isinstance(v, (datetime, date)) else None        
        
>>> bar = Bar('bar', Foo('foo', 1, 1/3, datetime.now(), datetime.now().date()))

>>> data = json.dumps(asdict(bar), default=datetime_to_str)

>>> Bar.from_data(json.loads(data))

Bar(name='bar', value=Foo(name='foo', int_value=1, float_value=0.3333333333333333, ts=datetime.datetime(2022, 8, 13, 12, 15, 44, 51572), dt=datetime.date(2022, 8, 13)))

>>> {bar: 1}

{Bar(name='bar', value=Foo(name='foo', int_value=1, float_value=0.3333333333333333, ts=datetime.datetime(2022, 8, 13, 12, 16, 45, 526179), dt=datetime.date(2022, 8, 13))): 1}
--------------
import gzip
import json
from dataclasses import dataclass, asdict

@dataclass(frozen=True, order=True)
class Foo:                                      
    name: str 
    int_value: int
    float_value: float
        
foos = [Foo('foo', 2, 1/3), Foo('foo', 1, 1/3)]

with gzip.open('foo.jsonl.gz', 'wt') as outfile:
    for foo in foos:
        outfile.write(json.dumps(asdict(foo)) + '\n')
        
new_foos = [
    Foo(**json.loads(row)) 
    for row in gzip.open('foo.jsonl.gz', 'rt')
]
--------------
from dataclasses import dataclass

@dataclass(frozen=True, order=True)
class Foo:                                      
    name: str 
    int_value: int
    float_value: float
        
>>> sorted([Foo('foo', 2, 1/3), Foo('foo', 1, 1/3)])
[Foo(name='foo', int_value=1, float_value=0.3333333333333333),
 Foo(name='foo', int_value=2, float_value=0.3333333333333333)]
--------------
from dataclasses import dataclass

@dataclass
class Foo:                                      
    name: str 
    int_value: int
    float_value: float
    
>>> Foo('foo', 1, 1/3)
Foo(name='foo', int_value=1, float_value=0.3333333333333333)
--------------
from dataclasses import dataclass

@dataclass
class Foo:                                      
    name: str 
    int_value: int
    float_value: float