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from contextlib import closing

from mysql.connector import connect


def get_data_for_grid(host, port, user, password, database, sql):
    with connect(
        host=host, port=port, user=user, password=password, database=database
    ) as connection:
        with connection.cursor() as cursor:
            cursor.execute(sql)
            return [
                tuple((str(item) if item is not None else "") for item in row)
                for row in cursor.fetchall()
            ]

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tuple((str(item) if item is not None else "") for item in row)

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#!/usr/bin/env python3
from contextlib import closing
from decimal import Decimal
from functools import singledispatch

import pytest
from mysql.connector import connect


@singledispatch
def convert_to_string(value):
    return str(value)


@convert_to_string.register(type(None))
def _convert_none(_value):
    return ""


@convert_to_string.register(float)
@convert_to_string.register(Decimal)
def _convert_number(value):
    return format(value, ".2f").replace(".", ",")


def get_data_for_grid(host, port, user, password, database, sql):
    with closing(
        connect(
            host=host,
            port=port,
            user=user,
            password=password,
            database=database,
        )
    ) as connection:
        with closing(connection.cursor()) as cursor:
            cursor.execute(sql)
            return [
                tuple(map(convert_to_string, row)) for row in cursor.fetchall()
            ]


@pytest.mark.parametrize(
    "value, expected",
    [
        ("test", "test"),
        (None, ""),
        (42, "42"),
        (2.3, "2,30"),
        (Decimal("4.2"), "4,20"),
    ],
)
def test_convert_to_string(value, expected):
    assert convert_to_string(value) == expected

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with closing(connection.cursor()) as cursor:
            cursor.execute(sql)