This is not a tutorial on editing the parse trees for Python code, but some examples of using the parser module are presented. Most importantly, a good understanding of the Python grammar processed by the internal parser is required. For full information on the language syntax, refer to the Python Language Reference . However, transporting code from one Python version to another as source text will always allow correct parse trees to be created in the target version, with the only restriction being that migrating to an older version of the interpreter will not support more recent language constructs. The parse trees are not typically compatible from one version to another, whereas source code has always been forward-compatible.
Sequences representing non-terminal elements in the grammar always have a length greater than one.
The first element is an integer which identifies a production in the grammar. Terminal elements are represented in much the same way, but without any child elements and the addition of the source text which was identified. The example of the if keyword above is representative. The parser module defines functions for a few distinct purposes. The most important purposes are to create AST objects and to convert AST objects to other representations such as parse trees and compiled code objects, but there are also functions which serve to query the type of parse tree represented by an AST object.