CODEWITHSUNDEEP
pythonwith-statement
Ian Fiddes
Ian Fiddes

Reputation: 3011

Building a class to use `with` to establish exclusive sql connections

I am working on a simple convenience class to use with the with operator so that I can establish exclusive access to a sqlite3 database for a extended writing session in a concurrent system.

Here is the class:

import sqlite3 as sql

class ExclusiveSqlConnection(object):
    """meant to be used with a with statement to ensure proper closure"""
    def __enter__(self, path):
        self.con = sql.connect(path, isolation_level = "EXCLUSIVE")
        self.con.execute("BEGIN EXCLUSIVE")
        self.cur = self.con.cursor()
        return self

    def __exit__(self):
        self.con.commit()
        self.con.close()

However, when I run this I get the error:

with sql_lib.ExclusiveSqlConnection(self.output) as c:
TypeError: object.__new__() takes no parameters

Upvotes: 1

Views: 47

Answers (1)

200_success
200_success

Reputation: 7591

The constructor (__init__ method) for your ExclusiveSqlConnection needs to take a path parameter.

On the other hand, __enter__ takes no parameter other than self.

import sqlite3 as sql

class ExclusiveSqlConnection(object):
    """meant to be used with a with statement to ensure proper closure"""

    def __init__(self, path):
        self.path = path

    def __enter__(self):
        self.con = sql.connect(self.path, isolation_level = "EXCLUSIVE")
        self.con.execute("BEGIN EXCLUSIVE")
        self.cur = self.con.cursor()
        return self

    def __exit__(self, exception_type, exception_val, trace):
        self.con.commit()
        self.con.close()

Upvotes: 2

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