migrations 0.0.3

Yet another Python migration tool

Simple, cross-database migration tool for Python applications. Inspired by node migrations.

Status

The project is in alpha now. Bugs and breaking changes will occur.

Requirements

Only Python 3 is supported for now.

Installation

$ pip install migrations

Notice, this distribution provides package and executable script named migrate, so check if it does not mess with existing packages/scripts. Generally, you should neither install this tool globally, nor install several migration tools for one project.

Features

TBD

Usage

usage: migrate [options] [action]

actions:
  up     [-h] [NAME|COUNT]   (default) perform COUNT migrations or till given NAME
                             (by default perform all available)
  down   [-h] [NAME|COUNT]   revert COUNT migrations or till given NAME
                             (by default revert one)
  create [-h]  NAME          create new migration file

options:
  -h, --help                 show this help message and exit
  -v, --version              show version and exit
  -d PATH, --migrations-dir PATH
                             directory where migrations are stored
  -s PATH, --state-file PATH
                             location of file which stores database state
  -t PATH, --template-file PATH
                             location of template file for new migrations

Each migration file must define functions up() and down() without required arguments.

Simple migration example:

import redis

db = redis.Redis(host='localhost', port=6379)

def up():
    db.rpush('used_libraries', 'migrations')

def down():
    db.rpop('used_libraries', 'migrations')

A bit more complex example. Let’s assume that in current working directory we have module named db, which contains singleton object responsible for DB connection, for example PyMySQL Connection object. Current working directory is the first place to be scanned for modules to import.

from db import connection

def manage_cursor(action):
    def wrap():
        with connection.cursor() as cursor:
            action(cursor)
        connection.commit()
    return wrap

@manage_cursor
def up(cursor):
    cursor.execute(
        "INSERT INTO used_libraries (`name`) VALUES ('migrations')"
    )

@manage_cursor
def down(cursor):
    cursor.execute(
        "DELETE FROM used_libraries WHERE `name`='migrations'"
    )