28. Python运行时服务
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本章里描述的模块提供了和Python解释器及其环境交互相关的广泛服务。以下是
综述：

* 28.1. "sys" — 系统相关的参数和函数

* 28.2. "sysconfig" — Provide access to Python’s configuration
  information

  * 28.2.1. 配置变量

  * 28.2.2. 安装路径

  * 28.2.3. 其他功能

* 28.3. "__builtin__" — Built-in objects

* 28.4. "future_builtins" — Python 3 builtins

* 28.5. "__main__" — 顶层脚本环境

* 28.6. "warnings" — Warning control

  * 28.6.1. 警告类别

  * 28.6.2. The Warnings Filter

    * 28.6.2.1. Default Warning Filters

  * 28.6.3. 暂时禁止警告

  * 28.6.4. 测试警告

  * 28.6.5. Updating Code For New Versions of Python

  * 28.6.6. Available Functions

  * 28.6.7. Available Context Managers

* 28.7. "contextlib" — Utilities for "with"-statement contexts

* 28.8. "abc" — 抽象基类

* 28.9. "atexit" — 退出处理器

  * 28.9.1. "atexit" 示例

* 28.10. "traceback" — 打印或检索堆栈回溯

  * 28.10.1. Traceback Examples

* 28.11. "__future__" — Future 语句定义

* 28.12. "gc" — 垃圾回收器接口

* 28.13. "inspect" — 检查对象

  * 28.13.1. 类型和成员

  * 28.13.2. Retrieving source code

  * 28.13.3. 类与函数

  * 28.13.4. The interpreter stack

* 28.14. "site" — Site-specific configuration hook

* 28.15. "user" — User-specific configuration hook

* 28.16. "fpectl" — Floating point exception control

  * 28.16.1. Example

  * 28.16.2. Limitations and other considerations
