nltk.tree.ParentedTree

class documentation

class ParentedTree(AbstractParentedTree): (source)

Known subclasses: nltk.tree.ImmutableParentedTree

Constructor: ParentedTree(node, children)

A Tree that automatically maintains parent pointers for single-parented trees. The following are methods for querying the structure of a parented tree: parent, parent_index, left_sibling, right_sibling, root, treeposition.

Each ParentedTree may have at most one parent. In particular, subtrees may not be shared. Any attempt to reuse a single ParentedTree as a child of more than one parent (or as multiple children of the same parent) will cause a ValueError exception to be raised.

ParentedTrees should never be used in the same tree as Trees or MultiParentedTrees. Mixing tree implementations may result in incorrect parent pointers and in TypeError exceptions.

Method	`__init__`	Undocumented
Method	`left_sibling`	The left sibling of this tree, or None if it has none.
Method	`parent`	The parent of this tree, or None if it has no parent.
Method	`parent_index`	The index of this tree in its parent. I.e., `ptree.parent()[ptree.parent_index()] is ptree`. Note that `ptree.parent_index()` is not necessarily equal to `ptree.parent.index(ptree)`, since the `index()` method returns the first child that is equal to its argument.
Method	`right_sibling`	The right sibling of this tree, or None if it has none.
Method	`root`	The root of this tree. I.e., the unique ancestor of this tree whose parent is None. If `ptree.parent()` is None, then `ptree` is its own root.
Method	`treeposition`	The tree position of this tree, relative to the root of the tree. I.e., `ptree.root[ptree.treeposition] is ptree`.
Method	`_delparent`	Update the parent pointer of `child` to not point to self. This method is only called if the type of `child` is `Tree`; i.e., it is not called when removing a leaf from a tree. This method is always called before the child is actually removed from the child list of ...
Method	`_frozen_class`	Undocumented
Method	`_setparent`	Update the parent pointer of `child` to point to `self`. This method is only called if the type of `child` is `Tree`; i.e., it is not called when adding a leaf to a tree. This method is always called before the child is actually added to the child list of ...
Instance Variable	`_parent`	The parent of this Tree, or None if it has no parent.

Inherited from AbstractParentedTree:

Method	`__delitem__`	Undocumented
Method	`__delslice__`	Undocumented
Method	`__getslice__`	Undocumented
Method	`__setitem__`	Undocumented
Method	`__setslice__`	Undocumented
Method	`append`	Undocumented
Method	`extend`	Undocumented
Method	`insert`	Undocumented
Method	`pop`	Undocumented
Method	`remove`	Undocumented

Inherited from Tree (via AbstractParentedTree):

Class Method	`convert`	Convert a tree between different subtypes of Tree. `cls` determines which class will be used to encode the new tree.
Class Method	`fromlist`	Convert nested lists to a NLTK Tree
Class Method	`fromstring`	Read a bracketed tree string and return the resulting tree. Trees are represented as nested brackettings, such as:
Method	`__add__`	Undocumented
Method	`__copy__`	Undocumented
Method	`__deepcopy__`	Undocumented
Method	`__eq__`	Undocumented
Method	`__getitem__`	Undocumented
Method	`__lt__`	Undocumented
Method	`__mul__`	Undocumented
Method	`__radd__`	Undocumented
Method	`__repr__`	Undocumented
Method	`__rmul__`	Undocumented
Method	`__str__`	Undocumented
Method	`chomsky_normal_form`	This method can modify a tree in three ways:
Method	`collapse_unary`	Collapse subtrees with a single child (ie. unary productions) into a new non-terminal (Tree node) joined by 'joinChar'. This is useful when working with algorithms that do not allow unary productions, and completely removing the unary productions would require loss of useful information...
Method	`copy`	Undocumented
Method	`draw`	Open a new window containing a graphical diagram of this tree.
Method	`flatten`	Return a flat version of the tree, with all non-root non-terminals removed.
Method	`freeze`	Undocumented
Method	`height`	Return the height of the tree.
Method	`label`	Return the node label of the tree.
Method	`leaf_treeposition`	No summary
Method	`leaves`	Return the leaves of the tree.
Method	`pformat`	No summary
Method	`pformat_latex_qtree`	Returns a representation of the tree compatible with the LaTeX qtree package. This consists of the string `\Tree` followed by the tree represented in bracketed notation.
Method	`pos`	Return a sequence of pos-tagged words extracted from the tree.
Method	`pprint`	Print a string representation of this Tree to 'stream'
Method	`pretty_print`	Pretty-print this tree as ASCII or Unicode art. For explanation of the arguments, see the documentation for `nltk.treeprettyprinter.TreePrettyPrinter`.
Method	`productions`	Generate the productions that correspond to the non-terminal nodes of the tree. For each subtree of the form (P: C1 C2 ... Cn) this produces a production of the form P -> C1 C2 ... Cn.
Method	`set_label`	Set the node label of the tree.
Method	`subtrees`	Generate all the subtrees of this tree, optionally restricted to trees matching the filter function.
Method	`treeposition_spanning_leaves`	No summary
Method	`treepositions`	No summary
Method	`un_chomsky_normal_form`	This method modifies the tree in three ways:
Class Variable	`__ge__`	Undocumented
Class Variable	`__gt__`	Undocumented
Class Variable	`__le__`	Undocumented
Class Variable	`__ne__`	Undocumented
Class Variable	`node`	Undocumented
Class Method	`_parse_error`	Display a friendly error message when parsing a tree string fails. :param s: The string we're parsing. :param match: regexp match of the problem token. :param expecting: what we expected to see instead.
Method	`_get_node`	Outdated method to access the node value; use the label() method instead.
Method	`_pformat_flat`	Undocumented
Method	`_repr_png_`	Draws and outputs in PNG for ipython. PNG is used instead of PDF, since it can be displayed in the qt console and has wider browser support.
Method	`_set_node`	Outdated method to set the node value; use the set_label() method instead.
Instance Variable	`_label`	Undocumented

def __init__(self, node, children=None): (source) ¶

overrides nltk.tree.AbstractParentedTree.__init__

Undocumented

def left_sibling(self): (source) ¶

The left sibling of this tree, or None if it has none.

def parent(self): (source) ¶

The parent of this tree, or None if it has no parent.

def parent_index(self): (source) ¶

The index of this tree in its parent. I.e., ptree.parent()[ptree.parent_index()] is ptree. Note that ptree.parent_index() is not necessarily equal to ptree.parent.index(ptree), since the index() method returns the first child that is equal to its argument.

def right_sibling(self): (source) ¶

The right sibling of this tree, or None if it has none.

def root(self): (source) ¶

The root of this tree. I.e., the unique ancestor of this tree whose parent is None. If ptree.parent() is None, then ptree is its own root.

def treeposition(self): (source) ¶

The tree position of this tree, relative to the root of the tree. I.e., ptree.root[ptree.treeposition] is ptree.

def _delparent(self, child, index): (source) ¶

overrides nltk.tree.AbstractParentedTree._delparent

Update the parent pointer of child to not point to self. This method is only called if the type of child is Tree; i.e., it is not called when removing a leaf from a tree. This method is always called before the child is actually removed from the child list of self.

Parameters
child:Tree	Undocumented
index:int	The index of `child` in `self`.

def _frozen_class(self): (source) ¶

overrides nltk.tree.Tree._frozen_class

Undocumented

def _setparent(self, child, index, dry_run=False): (source) ¶

overrides nltk.tree.AbstractParentedTree._setparent

Update the parent pointer of child to point to self. This method is only called if the type of child is Tree; i.e., it is not called when adding a leaf to a tree. This method is always called before the child is actually added to the child list of self.

Parameters
child:Tree	Undocumented
index:int	The index of `child` in `self`.
dry_run	If true, the don't actually set the child's parent pointer; just check for any error conditions, and raise an exception if one is found.
Raises
`TypeError`	If `child` is a tree with an impropriate type. Typically, if `child` is a tree, then its type needs to match the type of `self`. This prevents mixing of different tree types (single-parented, multi-parented, and non-parented).

_parent = (source) ¶

The parent of this Tree, or None if it has no parent.