# Chapter 43\. PL/Python - Python 過程語言 **Table of Contents** + 43.1\. Python 2 vs. Python 3 + 43.2\. PL/Python Functions + 43.3\. Data Values + 43.3.1\. Data Type Mapping + 43.3.2\. Null, None + 43.3.3\. Arrays, Lists + 43.3.4\. Composite Types + 43.3.5\. Set-returning Functions + 43.4\. Sharing Data + 43.5\. Anonymous Code Blocks + 43.6\. Trigger Functions + 43.7\. Database Access + 43.7.1\. Database Access Functions + 43.7.2\. Trapping Errors + 43.8\. Explicit Subtransactions + 43.8.1\. Subtransaction Context Managers + 43.8.2\. Older Python Versions + 43.9\. Utility Functions + 43.10\. Environment Variables PL/Python 過程語言允許用Python語言編寫 PostgreSQL 函數。 [Python 語言](http://www.python.org). 要在特定的數據庫里安裝PL/Python，使用 `CREATE EXTENSION plpythonu`，或者使用命令行工具 `createlang plpythonu` `_數據庫名稱_` （詳見[Section 43.1](#calibre_link-883)）。 > **Tip:** 如果一門語言安裝到了`template1`數據庫中，那么所有的隨后創建的數據庫都會自動的安裝該語言。 到目前為止PostgreSQL ， PL/Python 只能當成 一種"不可信任的" 語言，意思是他沒有提供任何限制用戶可為與不可為的手段，因此 他被重命令為 `plpythonu`，可信任的 `plpython` 可能在將來某個時間能夠獲得 if a new secure execution mechanism is developed in Python. The writer of a function in untrusted PL/Python must take care that the function cannot be used to do anything unwanted, since it will be able to do anything that could be done by a user logged in as the database administrator. Only superusers can create functions in untrusted languages such as `plpythonu`. > **Note:** Users of source packages must specially enable the build of PL/Python during the installation process. (Refer to the installation instructions for more information.) Users of binary packages might find PL/Python in a separate subpackage.