NoORM | SQL Construction library

noorm.py

from dataclasses import dataclass


@dataclass
class Query:
    db: object = None

    def sql(self):
        raise NotImplementedError

    def __call__(self):
        self.db.conn.execute(self.sql())


@dataclass
class Field:
    name: str
    table: object

    def __eq__(self, x):
        return f'{self.table}.{self.name} = {repr(x)}'

    def __str__(self):
        return f'{self.table}.{self.name}'


@dataclass
class Table:
    _name: str

    def __getattr__(self, name):
        f = Field(name, table=self)
        setattr(self, name, f)
        return f

    def __str__(self):
        return self._name


def Condition(NAME, things):
    return f'( {f" {NAME} ".join(things)} )'


def AND(*things):
    return Condition('AND', things)


def OR(*things):
    return Condition('OR', things)


@dataclass
class Select(Query):
    table = None
    op = 'SELECT'
    fields: list = None
    _limit: int = ''
    _where: str = ''

    def from_(self, table):
        self.table = table
        return self

    def limit(self, n=None):
        self._limit = f'LIMIT {n}' if n else ''
        return self

    def where(self, conds):
        if conds:
            self._where = f'WHERE {conds}'
        return self

    def sql(self):
        fields = f'{", ".join(str(f) for f in self.fields)}' if self.fields else '*'
        return f'{self.op} {fields} FROM {self.table} {self._where} {self._limit}'


class DB:

    def select(self, *fields):
        q = Select(db=self, fields=fields)
        return q


def test():
    db = DB()
    users = Table('users')
    q = db.select().from_(users)
    print(q.sql())
    q = db.select('name', 'email').from_(users).where(AND(users.name == 'Michael Scott').limit(1)
    print(q.sql())
    q = db.select('name', 'email').from_(users).where(AND(users.id == 7))).limit(1)
    print(q.sql())


if __name__ == '__main__':
    test()