Package TestON :: Package core :: Module ast
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Module ast

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ast
~~~

The `ast` module helps Python applications to process trees of the Python
abstract syntax grammar.  The abstract syntax itself might change with
each Python release; this module helps to find out programmatically what
the current grammar looks like and allows modifications of it.

An abstract syntax tree can be generated by passing `ast.PyCF_ONLY_AST` as
a flag to the `compile()` builtin function or by using the `parse()`
function from this module.  The result will be a tree of objects whose
classes all inherit from `ast.AST`.

A modified abstract syntax tree can be compiled into a Python code object
using the built-in `compile()` function.

Additionally various helper functions are provided that make working with
the trees simpler.  The main intention of the helper functions and this
module in general is to provide an easy to use interface for libraries
that work tightly with the python syntax (template engines for example).


:copyright: Copyright 2008 by Armin Ronacher.
:license: Python License.

Classes [hide private]
  NodeVisitor
A node visitor base class that walks the abstract syntax tree and calls a visitor function for every node found.
  NodeTransformer
A :class:`NodeVisitor` subclass that walks the abstract syntax tree and allows modification of nodes.
Functions [hide private]
 
parse(source, filename='<unknown>', mode='exec')
Parse the source into an AST node.
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literal_eval(node_or_string)
Safely evaluate an expression node or a string containing a Python expression.
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dump(node, annotate_fields=True, include_attributes=False)
Return a formatted dump of the tree in *node*.
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copy_location(new_node, old_node)
Copy source location (`lineno` and `col_offset` attributes) from *old_node* to *new_node* if possible, and return *new_node*.
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fix_missing_locations(node)
When you compile a node tree with compile(), the compiler expects lineno and col_offset attributes for every node that supports them.
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increment_lineno(node, n=1)
Increment the line number of each node in the tree starting at *node* by *n*.
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iter_fields(node)
Yield a tuple of ``(fieldname, value)`` for each field in ``node._fields`` that is present on *node*.
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iter_child_nodes(node)
Yield all direct child nodes of *node*, that is, all fields that are nodes and all items of fields that are lists of nodes.
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get_docstring(node, clean=True)
Return the docstring for the given node or None if no docstring can be found.
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walk(node)
Recursively yield all descendant nodes in the tree starting at *node* (including *node* itself), in no specified order.
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Function Details [hide private]

parse(source, filename='<unknown>', mode='exec')

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Parse the source into an AST node. Equivalent to compile(source, filename, mode, PyCF_ONLY_AST).

literal_eval(node_or_string)

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Safely evaluate an expression node or a string containing a Python expression. The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dicts, booleans, and None.

dump(node, annotate_fields=True, include_attributes=False)

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Return a formatted dump of the tree in *node*. This is mainly useful for debugging purposes. The returned string will show the names and the values for fields. This makes the code impossible to evaluate, so if evaluation is wanted *annotate_fields* must be set to False. Attributes such as line numbers and column offsets are not dumped by default. If this is wanted, *include_attributes* can be set to True.

fix_missing_locations(node)

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When you compile a node tree with compile(), the compiler expects lineno and col_offset attributes for every node that supports them. This is rather tedious to fill in for generated nodes, so this helper adds these attributes recursively where not already set, by setting them to the values of the parent node. It works recursively starting at *node*.

increment_lineno(node, n=1)

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Increment the line number of each node in the tree starting at *node* by *n*. This is useful to "move code" to a different location in a file.

get_docstring(node, clean=True)

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Return the docstring for the given node or None if no docstring can be found. If the node provided does not have docstrings a TypeError will be raised.

walk(node)

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Recursively yield all descendant nodes in the tree starting at *node* (including *node* itself), in no specified order. This is useful if you only want to modify nodes in place and don't care about the context.