# 18.3 `token` -- Constants used with Python parse trees

This module provides constants which represent the numeric values of leaf nodes of the parse tree (terminal tokens). Refer to the file Grammar/Grammar in the Python distribution for the definitions of the names in the context of the language grammar. The specific numeric values which the names map to may change between Python versions.

This module also provides one data object and some functions. The functions mirror definitions in the Python C header files.

`tok_name`
  Dictionary mapping the numeric values of the constants defined in this module back to name strings, allowing more human-readable representation of parse trees to be generated.

`ISTERMINAL`( | x)

  Return true for terminal token values.

`ISNONTERMINAL`( | x)

  Return true for non-terminal token values.

`ISEOF`( | x)

  Return true if x is the marker indicating the end of input.

See Also:

Module `parser`:
  The second example for the `parser` module shows how to use the `symbol` module.