Jun 28, 2013 MySQLdb is a Python DB API-2.0-compliant interface; see PEP-249 for details. For up-to-date versions of MySQLdb, use the homepage link. Supported versions:. MySQL versions from 3.23 to 5.5; 5.0 or newer recommended. MariaDB should also work. Python versions 2.4-2.7; Python 3 support coming soon. ZMySQLDA is a Database Adapter for Zope2. MySQL driver written in Python which does not depend on MySQL C client libraries and implements the DB API v2.0 specification (PEP-249). Project details. Homepage Download Statistics. View statistics for this project via Libraries.io, or by using our public dataset on Google BigQuery.
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The Python standard for database interfaces is the Python DB-API. Most Python database interfaces adhere to this standard.
You can choose the right database for your application. Python Database API supports a wide range of database servers such as −
- Microsoft SQL Server 2000
Here is the list of available Python database interfaces: Python Database Interfaces and APIs. You must download a separate DB API module for each database you need to access. For example, if you need to access an Oracle database as well as a MySQL database, you must download both the Oracle and the MySQL database modules.
The DB API provides a minimal standard for working with databases using Python structures and syntax wherever possible. This API includes the following −
- Importing the API module.
- Acquiring a connection with the database.
- Issuing SQL statements and stored procedures.
- Closing the connection
We would learn all the concepts using MySQL, so let us talk about MySQLdb module.
What is MySQLdb?
MySQLdb is an interface for connecting to a MySQL database server from Python. It implements the Python Database API v2.0 and is built on top of the MySQL C API.
How do I Install MySQLdb?
Before proceeding, you make sure you have MySQLdb installed on your machine. Just type the following in your Python script and execute it −
If it produces the following result, then it means MySQLdb module is not installed −
To install MySQLdb module, use the following command −
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Note − Make sure you have root privilege to install above module.
Before connecting to a MySQL database, make sure of the followings −
You have created a database TESTDB.
You have created a table EMPLOYEE in TESTDB.
This table has fields FIRST_NAME, LAST_NAME, AGE, SEX and INCOME.
User ID 'testuser' and password 'test123' are set to access TESTDB.
Python module MySQLdb is installed properly on your machine.
You have gone through MySQL tutorial to understand MySQL Basics.
Following is the example of connecting with MySQL database 'TESTDB'
While running this script, it is producing the following result in my Linux machine.
If a connection is established with the datasource, then a Connection Object is returned and saved into db for further use, otherwise db is set to None. Next, db object is used to create a cursor object, which in turn is used to execute SQL queries. Finally, before coming out, it ensures that database connection is closed and resources are released.
Creating Database Table
Once a database connection is established, we are ready to create tables or records into the database tables using execute method of the created cursor.
Let us create Database table EMPLOYEE −
It is required when you want to create your records into a database table.
The following example, executes SQL INSERT statement to create a record into EMPLOYEE table −
Above example can be written as follows to create SQL queries dynamically −
Following code segment is another form of execution where you can pass parameters directly −
READ Operation on any database means to fetch some useful information from the database.
Once our database connection is established, you are ready to make a query into this database. You can use either fetchone() method to fetch single record or fetchall() method to fetech multiple values from a database table.
fetchone() − It fetches the next row of a query result set. A result set is an object that is returned when a cursor object is used to query a table.
fetchall() − It fetches all the rows in a result set. If some rows have already been extracted from the result set, then it retrievesthe remaining rows from the result set.
rowcount − This is a read-only attribute and returns the number of rows that were affected by an execute() method.
The following procedure queries all the records from EMPLOYEE table having salary more than 1000 −
This will produce the following result −
UPDATE Operation on any database means to update one or more records, which are already available in the database.
The following procedure updates all the records having SEX as 'M'. Here, we increase AGE of all the males by one year.
DELETE operation is required when you want to delete some records from your database. Following is the procedure to delete all the records from EMPLOYEE where AGE is more than 20 −
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Transactions are a mechanism that ensures data consistency. Transactions have the following four properties −
Atomicity − Either a transaction completes or nothing happens at all.
Consistency − A transaction must start in a consistent state and leave the system in a consistent state.
Isolation − Intermediate results of a transaction are not visible outside the current transaction.
Durability − Once a transaction was committed, the effects are persistent, even after a system failure.
The Python DB API 2.0 provides two methods to either commit or rollback a transaction.
You already know how to implement transactions. Here is again similar example −
Commit is the operation, which gives a green signal to database to finalize the changes, and after this operation, no change can be reverted back.
Here is a simple example to call commit method.
If you are not satisfied with one or more of the changes and you want to revert back those changes completely, then use rollback() method.
Here is a simple example to call rollback() method.
To disconnect Database connection, use close() method.
If the connection to a database is closed by the user with the close() method, any outstanding transactions are rolled back by the DB. However, instead of depending on any of DB lower level implementation details, your application would be better off calling commit or rollback explicitly.
There are many sources of errors. A few examples are a syntax error in an executed SQL statement, a connection failure, or calling the fetch method for an already canceled or finished statement handle.
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The DB API defines a number of errors that must exist in each database module. The following table lists these exceptions.
|Sr.No.||Exception & Description|
Used for non-fatal issues. Must subclass StandardError.
Base class for errors. Must subclass StandardError.
Used for errors in the database module, not the database itself. Must subclass Error.
Used for errors in the database. Must subclass Error.
Subclass of DatabaseError that refers to errors in the data.
Subclass of DatabaseError that refers to errors such as the loss of a connection to the database. These errors are generally outside of the control of the Python scripter.
Subclass of DatabaseError for situations that would damage the relational integrity, such as uniqueness constraints or foreign keys.
Subclass of DatabaseError that refers to errors internal to the database module, such as a cursor no longer being active.
Subclass of DatabaseError that refers to errors such as a bad table name and other things that can safely be blamed on you.
Subclass of DatabaseError that refers to trying to call unsupported functionality.
Your Python scripts should handle these errors, but before using any of the above exceptions, make sure your MySQLdb has support for that exception. You can get more information about them by reading the DB API 2.0 specification.
You can get macOS PostgreSQL packages from several different sources.
Interactive installer by EDB
Download the installercertified by EDB for all supported PostgreSQL versions.
This installer includes the PostgreSQL server, pgAdmin; a graphical tool for managing and developingyour databases, and StackBuilder; a package manager that can be used to download and installadditional PostgreSQL tools and drivers. Stackbuilder includes management,integration, migration, replication, geospatial, connectors and other tools.
This installer can run in graphical, command line, or silent install modes.
The installer is designed to be a straightforward, fast way to get up and running withPostgreSQL on macOS.
Advanced users can also download azip archiveof the binaries, without the installer.This download is intended for users who wish to include PostgreSQL as part of another application installer.
The installers are tested by EDB on the following platforms. They will generally work on newer versions of macOS as well:
|PostgreSQL Version||64-bit macOS Platforms|
|13||10.13 - 10.15|
|12||10.12 - 10.14|
|11||10.12 - 10.14|
|10||10.10 - 10.12|
|9.6||10.10 - 10.12|
|9.5||10.8 - 10.10|
Postgres.app is a simple, native macOS app that runs in the menubar without the need of an installer. Open the app, and you have a PostgreSQL serverready and awaiting new connections. Close the app, and the server shuts down.
PostgreSQL can also be installed on macOSusing Homebrew. Please see the Homebrewdocumentation for information on how to install packages.
A listof PostgreSQLpackages can be found using the Braumeister search tool.
PostgreSQL packages are also available for macOS from theMacPorts Project. Please see theMacPorts documentation for information on how to install ports.
A list ofPostgreSQL packagescan be found using the portfiles search tool on the MacPorts website.
PostgreSQL packages are available for macOS from theFink Project.Please see the Fink documentation for information on how to install packages.
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A list ofPostgreSQL packagescan be found using the package search tool on the Fink website.