AST printing

Rationale

This package strives to provide some functionality missing from the ast module of the standard library, namely the pretty printing of AST objects:

• as a tree (essentially, the indented ast.dump());
• as a code snippet (which would give the tree back when being fed to ast.parse()).

There have been several packages containing implementations of one or both of these functions, among them:

• macropy ;
• meta ;
• astmonkey (based on the code by Armin Ronacher).

Unfortunately, all of them are not currently maintained, and do not fully support the changes introduced to ast in Python 3. The first two are also quite large and the required functionality plays a secondary role in them.

That is why this package was written. For the ease of maintenance it aims to be highly specialized and contain only the two functions specified above.

Usage

astprint.as_tree(node, indent='  ')

Returns a string with the ast.AST node pretty printed as a tree. When eval()'ed (with all the members of ast in the namespace), gives back the node.

astprint.as_code(node, indent='    ')

Returns a string with the ast.AST node pretty printed as a code snippet. When ast.parse()'ed, gives back the node.

Example

>>> import ast
>>> from astprint import as_code, as_tree
>>> code = """
... def func(x):
...     if x > 0:
...         return x
...     else:
...         return -x
... """
>>> node = ast.parse(code)
>>> print(as_code(node))
def func(x):
    if x > 0:
        return x
    else:
        return (-x)
>>> print(as_tree(node))
Module(body=[FunctionDef(
  args=arguments(
    args=[arg(
      annotation=None,
      arg='x')],
    defaults=[],
    kw_defaults=[],
    kwarg=None,
    kwargannotation=None,
    kwonlyargs=[],
    vararg=None,
    varargannotation=None),
  body=[If(
    body=[Return(value=Name(
      ctx=Load(),
      id='x'))],
    orelse=[Return(value=UnaryOp(
      op=USub(),
      operand=Name(
        ctx=Load(),
        id='x')))],
    test=Compare(
      comparators=[Num(n=0)],
      left=Name(
        ctx=Load(),
        id='x'),
      ops=[Gt()]))],
  decorator_list=[],
  name='func',
  returns=None)])