| \chapter{Python Services} | 
 |  | 
 | 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: | 
 |  | 
 | \begin{description} | 
 |  | 
 | \item[sys] | 
 | --- Access system specific parameters and functions. | 
 |  | 
 | \item[types] | 
 | --- Names for all built-in types. | 
 |  | 
 | \item[traceback] | 
 | --- Print or retrieve a stack traceback. | 
 |  | 
 | \item[pickle] | 
 | --- Convert Python objects to streams of bytes and back. | 
 |  | 
 | \item[shelve] | 
 | --- Python object persistency. | 
 |  | 
 | \item[copy] | 
 | --- Shallow and deep copy operations. | 
 |  | 
 | \item[marshal] | 
 | --- Convert Python objects to streams of bytes and back (with | 
 | different constraints). | 
 |  | 
 | \item[imp] | 
 | --- Access the implementation of the \code{import} statement. | 
 |  | 
 | \item[parser] | 
 | --- Retrieve and submit parse trees from and to the runtime support | 
 | environment. | 
 |  | 
 | \item[__builtin__] | 
 | --- The set of built-in functions. | 
 |  | 
 | \item[__main__] | 
 | --- The environment where the top-level script is run. | 
 |  | 
 | \end{description} |