I am looking for a pure-python SQL library that would give access to both MySQL and PostgreSQL.
The only requirement is to run on Python 2.5+ and be pure-python, so it can be included with the script and still run on most platforms (no-install).
In fact I am looking for a simple solution that would allow me to write SQL and export the results as CSV files.
Two part answer:
A) This is absolutely possible.
B) Depending on your exact concerns, a pure-python may or may not be a good approach to your problem.
Explained:
The SqlAlchemy library comes with two components : the more popular "ORM" , and the "Core" which it sits on top of. Either one will let you write your SQL commands in the SqlAlchemy format (which is just Python); SqlAlchemy will then compile the statements to Mysql or PostgreSQL and connect to the appropriate database.
SqlAlchemy is a great library, and I recommend it for just about everything. While you do have to write your statements in their format, it's easy to pick up -- and you can switch to virtually any underlying database library you want... at any time. It's the perfect platform to use in any database project , whether or not you need to support multiple backends.
SqlAlchemy talks to the database via the standard DBAPI drivers, and does support multiple options for pure python, notably the pymysql and pypostgresql drivers ( http://docs.sqlalchemy.org/en/latest/core/engines.html#supported-dbapis )
As for writing csv, the standard library has you covered.
import csv
So the caveat?
The following may or may not apply to your situation:
Most higher level db modules in the python universe are still recommending mysql-python and psycopg - both of which are not pure-python and compile/link/configure against the installed database. This largely seems to be from a mix of API / integration concerns and the speed of the various pure-python packages compared to c-extensions when run under CPython.
There are pure-python drivers like I recommended, but most reviewers state that they're largely experimental. The pymysql authors claim stability and production readiness, some developers who blog have challenged that. As for what "stabile" or "experimental" means, that varies with the projects. Some have a changing API, others are incomplete, some are buggy.
You'd need to ensure that you can find pure-python drivers for each system that support the exact operations you need. This could be simple, or this could be messy. Whether you use SqlAlchemy or something else, you'll still face this concern when selecting a DBAPI driver.
The PyPy project ( pure-python python interpreter ) has a wiki listing the compatibility of various packages : https://bitbucket.org/pypy/compatibility/wiki/Home I would defer to them for specific driver suggestions. If PyPy is your intended platform, SqlAlchemy runs perfectly on it as well.
Are you looking for an ORM, or a single library that would allow you to write SQL statements directly and convert where there are differences?
I'm not sure whether psycopg2 is pure-python or not, but it certainly has bindings and works on all platforms. You'd still have to install at least psycopg2 to communicate with the PostgreSQL database as Python (as far as I know) doesn't ship with it natively.
From there, any additional ORM library you want would also need to be installed, but most are pure-python on-top of whatever backend they use.
Storm, Django, SQLAlchemy all have abstracted layers on top of their database layer - based on your description, Django is probably too large a framework for your needs (was for mine) but is a popular one, SQLAlchemy is a tried and true system - tho a bit clunky particularly if you have to deal with inheritance (in my opinion). I have heard that Storm is good, tho I haven't tested too much with it so I can't fully say.
If you are looking to mix and match (some tables in MySQL and some tables in PostgreSQL) vs. a single database that could be either MySQL or PostgreSQL, I've been working on an ORM called ORB that focuses more on object-oriented design and allows for multiple databases and relationships between databases. Right now it only supports PostgreSQL and Mongo, just cause I haven't needed MySQL, but I'd be up for writing that backend. The code for that can be found at http://docs.projexsoftware.com/api/orb
Use SQL-Alchemy. It will work with most database types, and certainly does work with postgres and MySQL.
Related
I'm trying to implement the python DB-API for a small "database" that we built internally. This database does not expose an ODBC interface (or JDBC for that matter). My goal is to create a sqlalchemy for this so that I can use it with an application like Superset for example. I have created JDBC drivers in the past and that requires full Java implementation of the methods from the interfaces. In case of Python's DB-API, I couldn't find any example. Even the one I saw with psycopg2 https://github.com/psycopg/psycopg2 is fully written in C and I'm not an expert on C.
Any way to implement the DB-API only in python? Is there any examples available? (Sorry if my understanding of db-api is not correct.)
You can find plenty of DB-API drivers written in Python. The specific libraries depend on how your database communicates and packs/unpacks data.
If you're database is listening on a port, you'll probably be using the socket module.
If you're doing any kind of batch inserting or unpacking, you want to check out the struct module as well.
If you don't need support for Python 2, with Python 3.3+ you get memoryview().cast(), which may also come handy with regard to unpacking data.
Python 3.8 comes with the shared memory module, which can help you out when you start optimizing.
If your database runs on a specific platform, ctypes comes handy for pulling out OS specific tweaks (Like manually implementing shared memory if you can't use Python 3.8).
Pandas used to support DB-API connections directly. It currently only supports the SQlite DB-API officially, but you can piggyback it, which will allow you to test yourself with a known tool.
Is there any library or tool to perform database migrations in python without SQLAlchemy? I am using a PostgreSQL database and the queries are raw SQL. I use psycopg2 for the database connection.
In short, "yes."
There are numerous possibilities. The one you choose will depend on doing some homework to determine which one best suits your needs.
https://github.com/amacneil/dbmate
https://pypi.org/project/yoyo-migrations/
https://pypi.org/project/alembic/
Suggest when asking questions that can be answered with a google search, to be more specific about your situation, to help answerers to understand why Google couldn't answer your question in the first page of results.
If you can bring yourself to do your db migrations outside of the CLR, I'd strongly recommend considering FlyWay. It has been around forever, it's supported by RedGate, and the community version is free and open source. It has built-in support for all the major db platforms and installs like any other utility you'd use. For a Python app you'd do all of your db migrations via shell scripts or process calls instead of directly in the code.
My team settled on this tech because:
Yoyo is pretty immature and buggy for us
We don't use SQLAlchemy's OR framework
Alembic's syntax and framework seems pretty heavyweight for us
Under FlyWay's model we just write SQL scripts and check them into a directory. It's really lightweight.
It's been proven to work nicely in clustered environments
Give it a look.
im working on python application that requiring database connections..I had developed my application with sqlite3 but it start showing the error(the database is locked).. so I decided to use MySQL database instead.. and it is pretty good with no error..
the only one problem is that I need to ask every user using my application to install MySQL server on his pc (appserv for example) ..
so can I make mysql to be like sqlite3 apart of python lib. so I can produce a python script can be converted into exe file by the tool pyInstaller.exe and no need to install mysql server by users???
update:
after reviewing the code I found opened connection not closed correctly and work fine with sqllite3 ..thank you every body
It depends (more "depends" in the answer).
If you need to share the data between the users of your application - you need a mysql database server somewhere setup, your application would need to have an access to it. And, the performance can really depend on the network - depends on how heavily would the application use the database. The application itself would only need to know how to "speak" with the database server - python mysql driver, like MySQLdb or pymysql.
If you don't need to share the data between users - then sqlite may be an option. Or may be not - depends on what do you want to store there, what for and what do you need to do with the data.
So, more questions than answers, probably it was more suitable for a comment. At least, think about what I've said.
Also see:
https://stackoverflow.com/questions/1009438/which-database-should-i-use-for-my-desktop-application
Python Desktop Application Database
Python Framework for Desktop Database Application
Hope that helps.
If your application is a stand-alone system such that each user maintains their own private database then you have no alternative to install MySQL on each system that is running the application. You cannot bundle MySQL into your application such that it does not require a separate installation.
There is an embedded version of MySQL that you can build into your application (thanks, Carsten, in the comments, for pointing this out). More information is here: http://mysql-python.blogspot.com/. It may take some effort to get this working (on Windows you apparently need to build it from source code) and will take some more work to get it packaged up when you generate your executable, but this might be a MySQL solution for you.
I've just finished updating a web application using SQLite which had begun reporting Database is locked errors as the usage scaled up. By rewriting the database code with care I was able to produce a system that can handle moderate to heavy usage (in the context of a 15 person company) reliably still using SQLite -- you have to be careful to keep your connections around for the minimum time necessary and always call .close() on them. If your application is really single-user you should have no problem supporting it using SQLite -- and that's doubly true if it's single-threaded.
I'm currently exploring using python to develop my server-side implementation. I've decided to use SQLAlchemy for database stuff.
What I'm not currently to sure about is how it should be set up so that more than one developer can work on the project. For the code it is not a problem but how do I handle the database modifications? How do the users sync databases and how should potential data be set up? Should/can each developer use their own sqlite db for development?
For production postgresql will be used but the developers must be able to work offline.
You can use Alembic to manage your DB structure. Keep your migrations under version control in order to ensure that it's easy for developers to keep in sync with changes.
As regards data itself, you can either work with a set of fixtures, or you could write some Fabric commands to import/export Postgres dumps, which you could also keep under version control if necessary – depending on data size, you may not want to keep a large uncompressed SQL dump under version control (though it will compress well using git or hg), however. This aspect of your question depends on the size of your development team, and the size of your database.
Make sure you have a python programs or programs to fill databases with test data from scratch. It allows each developer to work from different starting points, but also test with the same environment.
i am new in python.before this i done some work in php with codeigniter framework.
now i want to develop website using python and sqlite3.
so which framework will you suggest me.
i also want to know IDE for sqlite.
Do you mean something similar to sqliteman or dbeaver? These are not not IDEs for SQLite, but instead, are GUI interfaces. There are more here: http://www.google.com/search?&q=sqlite+gui
3rd link down is another stack overflow question: What are good open source GUI SQLite database managers?
For Python web frameworks, a very popular full-stack framework is the Django Project
Check out web2py. It's a feature-rich full-stack framework, but it's also very easy to set up, learn, and use. It requires no installation or configuration, has no dependencies, and includes its own web server and web-based IDE/administrative interface (see demo). If you download the binary version for Windows or Mac, it even includes its own Python interpreter (so you don't need to have Python installed).
The database abstraction layer (DAL) works with 10 different database backends, including SQLite. It doesn't include its own SQLite IDE, though it does include a database administrative interface called appadmin, which allows you to view all database tables; view, insert, update, and delete records within each table; and import/export tables to CSV. You can also import and export the entire database to CSV. (Note, these features work for all database backends, not just SQLite.)
You will probably also find that you don't really need an IDE for SQLite when using web2py because the DAL takes care of everything for you. You specify all of your data models using the DAL syntax, and then the DAL automatically creates the SQLite database, creates all tables, and handles migrations when you changes your models.
If you have any questions, there's a friendly and responsive mailing list that will provide lots of help.