The modules described in this chapter provide a wide range of services related to the Python interpreter and its interaction with its environment. Here's an overview:
| sys | Access system-specific parameters and functions. | 
| gc | Interface to the cycle-detecting garbage collector. | 
| atexit | Register and execute cleanup functions. | 
| types | Names for all built-in types. | 
| UserDict | Class wrapper for dictionary objects. | 
| UserList | Class wrapper for list objects. | 
| UserString | Class wrapper for string objects. | 
| operator | All Python's standard operators as built-in functions. | 
| traceback | Print or retrieve a stack traceback. | 
| linecache | This module provides random access to individual lines from text files. | 
| pickle | Convert Python objects to streams of bytes and back. | 
| cPickle | Faster version of pickle, but not subclassable. | 
| copy_reg | Register pickle support functions. | 
| shelve | Python object persistence. | 
| copy | Shallow and deep copy operations. | 
| marshal | Convert Python objects to streams of bytes and back (with different constraints). | 
| imp | Access the implementation of the import statement. | 
| code | Base classes for interactive Python interpreters. | 
| codeop | Compile (possibly incomplete) Python code. | 
| pprint | Data pretty printer. | 
| repr | Alternate repr() implementation with size limits. | 
| new | Interface to the creation of runtime implementation objects. | 
| site | A standard way to reference site-specific modules. | 
| user | A standard way to reference user-specific modules. | 
| __builtin__ | The set of built-in functions. | 
| __main__ | The environment where the top-level script is run. |