# Natural Language Toolkit: ASCII visualization of NLTK trees # # Copyright (C) 2001-2024 NLTK Project # Author: Andreas van Cranenburgh # Peter Ljunglöf # URL: # For license information, see LICENSE.TXT """ Pretty-printing of discontinuous trees. Adapted from the disco-dop project, by Andreas van Cranenburgh. https://github.com/andreasvc/disco-dop Interesting reference (not used for this code): T. Eschbach et al., Orth. Hypergraph Drawing, Journal of Graph Algorithms and Applications, 10(2) 141--157 (2006)149. https://jgaa.info/accepted/2006/EschbachGuentherBecker2006.10.2.pdf """ import re try: from html import escape except ImportError: from cgi import escape from collections import defaultdict from operator import itemgetter from nltk.tree.tree import Tree from nltk.util import OrderedDict ANSICOLOR = { "black": 30, "red": 31, "green": 32, "yellow": 33, "blue": 34, "magenta": 35, "cyan": 36, "white": 37, } class TreePrettyPrinter: """ Pretty-print a tree in text format, either as ASCII or Unicode. The tree can be a normal tree, or discontinuous. ``TreePrettyPrinter(tree, sentence=None, highlight=())`` creates an object from which different visualizations can be created. :param tree: a Tree object. :param sentence: a list of words (strings). If `sentence` is given, `tree` must contain integers as leaves, which are taken as indices in `sentence`. Using this you can display a discontinuous tree. :param highlight: Optionally, a sequence of Tree objects in `tree` which should be highlighted. Has the effect of only applying colors to nodes in this sequence (nodes should be given as Tree objects, terminals as indices). >>> from nltk.tree import Tree >>> tree = Tree.fromstring('(S (NP Mary) (VP walks))') >>> print(TreePrettyPrinter(tree).text()) ... # doctest: +NORMALIZE_WHITESPACE S ____|____ NP VP | | Mary walks """ def __init__(self, tree, sentence=None, highlight=()): if sentence is None: leaves = tree.leaves() if ( leaves and all(len(a) > 0 for a in tree.subtrees()) and all(isinstance(a, int) for a in leaves) ): sentence = [str(a) for a in leaves] else: # this deals with empty nodes (frontier non-terminals) # and multiple/mixed terminals under non-terminals. tree = tree.copy(True) sentence = [] for a in tree.subtrees(): if len(a) == 0: a.append(len(sentence)) sentence.append(None) elif any(not isinstance(b, Tree) for b in a): for n, b in enumerate(a): if not isinstance(b, Tree): a[n] = len(sentence) if type(b) == tuple: b = "/".join(b) sentence.append("%s" % b) self.nodes, self.coords, self.edges, self.highlight = self.nodecoords( tree, sentence, highlight ) def __str__(self): return self.text() def __repr__(self): return "" % len(self.nodes) @staticmethod def nodecoords(tree, sentence, highlight): """ Produce coordinates of nodes on a grid. Objective: - Produce coordinates for a non-overlapping placement of nodes and horizontal lines. - Order edges so that crossing edges cross a minimal number of previous horizontal lines (never vertical lines). Approach: - bottom up level order traversal (start at terminals) - at each level, identify nodes which cannot be on the same row - identify nodes which cannot be in the same column - place nodes into a grid at (row, column) - order child-parent edges with crossing edges last Coordinates are (row, column); the origin (0, 0) is at the top left; the root node is on row 0. Coordinates do not consider the size of a node (which depends on font, &c), so the width of a column of the grid should be automatically determined by the element with the greatest width in that column. Alternatively, the integer coordinates could be converted to coordinates in which the distances between adjacent nodes are non-uniform. Produces tuple (nodes, coords, edges, highlighted) where: - nodes[id]: Tree object for the node with this integer id - coords[id]: (n, m) coordinate where to draw node with id in the grid - edges[id]: parent id of node with this id (ordered dictionary) - highlighted: set of ids that should be highlighted """ def findcell(m, matrix, startoflevel, children): """ Find vacant row, column index for node ``m``. Iterate over current rows for this level (try lowest first) and look for cell between first and last child of this node, add new row to level if no free row available. """ candidates = [a for _, a in children[m]] minidx, maxidx = min(candidates), max(candidates) leaves = tree[m].leaves() center = scale * sum(leaves) // len(leaves) # center of gravity if minidx < maxidx and not minidx < center < maxidx: center = sum(candidates) // len(candidates) if max(candidates) - min(candidates) > 2 * scale: center -= center % scale # round to unscaled coordinate if minidx < maxidx and not minidx < center < maxidx: center += scale if ids[m] == 0: startoflevel = len(matrix) for rowidx in range(startoflevel, len(matrix) + 1): if rowidx == len(matrix): # need to add a new row matrix.append( [ vertline if a not in (corner, None) else None for a in matrix[-1] ] ) row = matrix[rowidx] if len(children[m]) == 1: # place unaries directly above child return rowidx, next(iter(children[m]))[1] elif all( a is None or a == vertline for a in row[min(candidates) : max(candidates) + 1] ): # find free column for n in range(scale): i = j = center + n while j > minidx or i < maxidx: if i < maxidx and ( matrix[rowidx][i] is None or i in candidates ): return rowidx, i elif j > minidx and ( matrix[rowidx][j] is None or j in candidates ): return rowidx, j i += scale j -= scale raise ValueError( "could not find a free cell for:\n%s\n%s" "min=%d; max=%d" % (tree[m], minidx, maxidx, dumpmatrix()) ) def dumpmatrix(): """Dump matrix contents for debugging purposes.""" return "\n".join( "%2d: %s" % (n, " ".join(("%2r" % i)[:2] for i in row)) for n, row in enumerate(matrix) ) leaves = tree.leaves() if not all(isinstance(n, int) for n in leaves): raise ValueError("All leaves must be integer indices.") if len(leaves) != len(set(leaves)): raise ValueError("Indices must occur at most once.") if not all(0 <= n < len(sentence) for n in leaves): raise ValueError( "All leaves must be in the interval 0..n " "with n=len(sentence)\ntokens: %d indices: " "%r\nsentence: %s" % (len(sentence), tree.leaves(), sentence) ) vertline, corner = -1, -2 # constants tree = tree.copy(True) for a in tree.subtrees(): a.sort(key=lambda n: min(n.leaves()) if isinstance(n, Tree) else n) scale = 2 crossed = set() # internal nodes and lexical nodes (no frontiers) positions = tree.treepositions() maxdepth = max(map(len, positions)) + 1 childcols = defaultdict(set) matrix = [[None] * (len(sentence) * scale)] nodes = {} ids = {a: n for n, a in enumerate(positions)} highlighted_nodes = { n for a, n in ids.items() if not highlight or tree[a] in highlight } levels = {n: [] for n in range(maxdepth - 1)} terminals = [] for a in positions: node = tree[a] if isinstance(node, Tree): levels[maxdepth - node.height()].append(a) else: terminals.append(a) for n in levels: levels[n].sort(key=lambda n: max(tree[n].leaves()) - min(tree[n].leaves())) terminals.sort() positions = set(positions) for m in terminals: i = int(tree[m]) * scale assert matrix[0][i] is None, (matrix[0][i], m, i) matrix[0][i] = ids[m] nodes[ids[m]] = sentence[tree[m]] if nodes[ids[m]] is None: nodes[ids[m]] = "..." highlighted_nodes.discard(ids[m]) positions.remove(m) childcols[m[:-1]].add((0, i)) # add other nodes centered on their children, # if the center is already taken, back off # to the left and right alternately, until an empty cell is found. for n in sorted(levels, reverse=True): nodesatdepth = levels[n] startoflevel = len(matrix) matrix.append( [vertline if a not in (corner, None) else None for a in matrix[-1]] ) for m in nodesatdepth: # [::-1]: if n < maxdepth - 1 and childcols[m]: _, pivot = min(childcols[m], key=itemgetter(1)) if { a[:-1] for row in matrix[:-1] for a in row[:pivot] if isinstance(a, tuple) } & { a[:-1] for row in matrix[:-1] for a in row[pivot:] if isinstance(a, tuple) }: crossed.add(m) rowidx, i = findcell(m, matrix, startoflevel, childcols) positions.remove(m) # block positions where children of this node branch out for _, x in childcols[m]: matrix[rowidx][x] = corner # assert m == () or matrix[rowidx][i] in (None, corner), ( # matrix[rowidx][i], m, str(tree), ' '.join(sentence)) # node itself matrix[rowidx][i] = ids[m] nodes[ids[m]] = tree[m] # add column to the set of children for its parent if len(m) > 0: childcols[m[:-1]].add((rowidx, i)) assert len(positions) == 0 # remove unused columns, right to left for m in range(scale * len(sentence) - 1, -1, -1): if not any(isinstance(row[m], (Tree, int)) for row in matrix): for row in matrix: del row[m] # remove unused rows, reverse matrix = [ row for row in reversed(matrix) if not all(a is None or a == vertline for a in row) ] # collect coordinates of nodes coords = {} for n, _ in enumerate(matrix): for m, i in enumerate(matrix[n]): if isinstance(i, int) and i >= 0: coords[i] = n, m # move crossed edges last positions = sorted( (a for level in levels.values() for a in level), key=lambda a: a[:-1] in crossed, ) # collect edges from node to node edges = OrderedDict() for i in reversed(positions): for j, _ in enumerate(tree[i]): edges[ids[i + (j,)]] = ids[i] return nodes, coords, edges, highlighted_nodes def text( self, nodedist=1, unicodelines=False, html=False, ansi=False, nodecolor="blue", leafcolor="red", funccolor="green", abbreviate=None, maxwidth=16, ): """ :return: ASCII art for a discontinuous tree. :param unicodelines: whether to use Unicode line drawing characters instead of plain (7-bit) ASCII. :param html: whether to wrap output in html code (default plain text). :param ansi: whether to produce colors with ANSI escape sequences (only effective when html==False). :param leafcolor, nodecolor: specify colors of leaves and phrasal nodes; effective when either html or ansi is True. :param abbreviate: if True, abbreviate labels longer than 5 characters. If integer, abbreviate labels longer than `abbr` characters. :param maxwidth: maximum number of characters before a label starts to wrap; pass None to disable. """ if abbreviate == True: abbreviate = 5 if unicodelines: horzline = "\u2500" leftcorner = "\u250c" rightcorner = "\u2510" vertline = " \u2502 " tee = horzline + "\u252C" + horzline bottom = horzline + "\u2534" + horzline cross = horzline + "\u253c" + horzline ellipsis = "\u2026" else: horzline = "_" leftcorner = rightcorner = " " vertline = " | " tee = 3 * horzline cross = bottom = "_|_" ellipsis = "." def crosscell(cur, x=vertline): """Overwrite center of this cell with a vertical branch.""" splitl = len(cur) - len(cur) // 2 - len(x) // 2 - 1 lst = list(cur) lst[splitl : splitl + len(x)] = list(x) return "".join(lst) result = [] matrix = defaultdict(dict) maxnodewith = defaultdict(lambda: 3) maxnodeheight = defaultdict(lambda: 1) maxcol = 0 minchildcol = {} maxchildcol = {} childcols = defaultdict(set) labels = {} wrapre = re.compile( "(.{%d,%d}\\b\\W*|.{%d})" % (maxwidth - 4, maxwidth, maxwidth) ) # collect labels and coordinates for a in self.nodes: row, column = self.coords[a] matrix[row][column] = a maxcol = max(maxcol, column) label = ( self.nodes[a].label() if isinstance(self.nodes[a], Tree) else self.nodes[a] ) if abbreviate and len(label) > abbreviate: label = label[:abbreviate] + ellipsis if maxwidth and len(label) > maxwidth: label = wrapre.sub(r"\1\n", label).strip() label = label.split("\n") maxnodeheight[row] = max(maxnodeheight[row], len(label)) maxnodewith[column] = max(maxnodewith[column], max(map(len, label))) labels[a] = label if a not in self.edges: continue # e.g., root parent = self.edges[a] childcols[parent].add((row, column)) minchildcol[parent] = min(minchildcol.get(parent, column), column) maxchildcol[parent] = max(maxchildcol.get(parent, column), column) # bottom up level order traversal for row in sorted(matrix, reverse=True): noderows = [ ["".center(maxnodewith[col]) for col in range(maxcol + 1)] for _ in range(maxnodeheight[row]) ] branchrow = ["".center(maxnodewith[col]) for col in range(maxcol + 1)] for col in matrix[row]: n = matrix[row][col] node = self.nodes[n] text = labels[n] if isinstance(node, Tree): # draw horizontal branch towards children for this node if n in minchildcol and minchildcol[n] < maxchildcol[n]: i, j = minchildcol[n], maxchildcol[n] a, b = (maxnodewith[i] + 1) // 2 - 1, maxnodewith[j] // 2 branchrow[i] = ((" " * a) + leftcorner).ljust( maxnodewith[i], horzline ) branchrow[j] = (rightcorner + (" " * b)).rjust( maxnodewith[j], horzline ) for i in range(minchildcol[n] + 1, maxchildcol[n]): if i == col and any(a == i for _, a in childcols[n]): line = cross elif i == col: line = bottom elif any(a == i for _, a in childcols[n]): line = tee else: line = horzline branchrow[i] = line.center(maxnodewith[i], horzline) else: # if n and n in minchildcol: branchrow[col] = crosscell(branchrow[col]) text = [a.center(maxnodewith[col]) for a in text] color = nodecolor if isinstance(node, Tree) else leafcolor if isinstance(node, Tree) and node.label().startswith("-"): color = funccolor if html: text = [escape(a, quote=False) for a in text] if n in self.highlight: text = [f"{a}" for a in text] elif ansi and n in self.highlight: text = ["\x1b[%d;1m%s\x1b[0m" % (ANSICOLOR[color], a) for a in text] for x in range(maxnodeheight[row]): # draw vertical lines in partially filled multiline node # labels, but only if it's not a frontier node. noderows[x][col] = ( text[x] if x < len(text) else (vertline if childcols[n] else " ").center( maxnodewith[col], " " ) ) # for each column, if there is a node below us which has a parent # above us, draw a vertical branch in that column. if row != max(matrix): for n, (childrow, col) in self.coords.items(): if n > 0 and self.coords[self.edges[n]][0] < row < childrow: branchrow[col] = crosscell(branchrow[col]) if col not in matrix[row]: for noderow in noderows: noderow[col] = crosscell(noderow[col]) branchrow = [ a + ((a[-1] if a[-1] != " " else b[0]) * nodedist) for a, b in zip(branchrow, branchrow[1:] + [" "]) ] result.append("".join(branchrow)) result.extend( (" " * nodedist).join(noderow) for noderow in reversed(noderows) ) return "\n".join(reversed(result)) + "\n" def svg(self, nodecolor="blue", leafcolor="red", funccolor="green"): """ :return: SVG representation of a tree. """ fontsize = 12 hscale = 40 vscale = 25 hstart = vstart = 20 width = max(col for _, col in self.coords.values()) height = max(row for row, _ in self.coords.values()) result = [ '' % ( width * 3, height * 2.5, -hstart, -vstart, width * hscale + 3 * hstart, height * vscale + 3 * vstart, ) ] children = defaultdict(set) for n in self.nodes: if n: children[self.edges[n]].add(n) # horizontal branches from nodes to children for node in self.nodes: if not children[node]: continue y, x = self.coords[node] x *= hscale y *= vscale x += hstart y += vstart + fontsize // 2 childx = [self.coords[c][1] for c in children[node]] xmin = hstart + hscale * min(childx) xmax = hstart + hscale * max(childx) result.append( '\t' % (xmin, y, xmax, y) ) result.append( '\t' % (x, y, x, y - fontsize // 3) ) # vertical branches from children to parents for child, parent in self.edges.items(): y, _ = self.coords[parent] y *= vscale y += vstart + fontsize // 2 childy, childx = self.coords[child] childx *= hscale childy *= vscale childx += hstart childy += vstart - fontsize result += [ '\t' % (childx, childy, childx, y + 5), '\t' % (childx, childy, childx, y), ] # write nodes with coordinates for n, (row, column) in self.coords.items(): node = self.nodes[n] x = column * hscale + hstart y = row * vscale + vstart if n in self.highlight: color = nodecolor if isinstance(node, Tree) else leafcolor if isinstance(node, Tree) and node.label().startswith("-"): color = funccolor else: color = "black" result += [ '\t%s' % ( color, fontsize, x, y, escape( node.label() if isinstance(node, Tree) else node, quote=False ), ) ] result += [""] return "\n".join(result) def test(): """Do some tree drawing tests.""" def print_tree(n, tree, sentence=None, ansi=True, **xargs): print() print('{}: "{}"'.format(n, " ".join(sentence or tree.leaves()))) print(tree) print() drawtree = TreePrettyPrinter(tree, sentence) try: print(drawtree.text(unicodelines=ansi, ansi=ansi, **xargs)) except (UnicodeDecodeError, UnicodeEncodeError): print(drawtree.text(unicodelines=False, ansi=False, **xargs)) from nltk.corpus import treebank for n in [0, 1440, 1591, 2771, 2170]: tree = treebank.parsed_sents()[n] print_tree(n, tree, nodedist=2, maxwidth=8) print() print("ASCII version:") print(TreePrettyPrinter(tree).text(nodedist=2)) tree = Tree.fromstring( "(top (punct 8) (smain (noun 0) (verb 1) (inf (verb 5) (inf (verb 6) " "(conj (inf (pp (prep 2) (np (det 3) (noun 4))) (verb 7)) (inf (verb 9)) " "(vg 10) (inf (verb 11)))))) (punct 12))", read_leaf=int, ) sentence = ( "Ze had met haar moeder kunnen gaan winkelen ," " zwemmen of terrassen .".split() ) print_tree("Discontinuous tree", tree, sentence, nodedist=2) __all__ = ["TreePrettyPrinter"] if __name__ == "__main__": test()