Moved graph unicode signs outside the function and applied pep8.

graph.py

 # vim: set fileencoding=utf-8 :
 # XXX Used in doctests (we should use them in the __main__ section below too).
+
+PIPE_SIGN = '│'.decode('utf-8')
+DASH_SIGN = '─'.decode('utf-8')
+CROSS_SIGN = '┼'.decode('utf-8')
+TSPLIT_DN_SIGN = '┬'.decode('utf-8')
+TSPLIT_UP_SIGN = '┴'.decode('utf-8')
+LEFT_SIGN = '╭'.decode('utf-8')
+RIGHT_SIGN = '╮'.decode('utf-8')
+
+
 def generate_graph(root, separator=' ', verbose=False):
     """
     Return a text-based, utf-8 graph of a tree-like structure. Each tree node
@@ -112,49 +122,39 @@ def generate_graph(root, separator=' ', verbose=False):
         box_widths = [len(lines[0]) for lines in child_lines]
         node_len = len(node)
         middle_node = int(node_len / 2)
-        #middle = sum([box_widths[i] for i in range(middle_node)]) \
-        #         + max(middle_node - int(node_len % 2 == 0), 0) * separator_len
         middle = node_middle[node]
 
         title_line = center_text(node.title(), line_width, middle)
 
-        pipe_sign = '│'.decode('utf-8')
-        dash_sign = '─'.decode('utf-8')
-        cross_sign = '┼'.decode('utf-8')
-        tsplit_dn_sign = '┬'.decode('utf-8')
-        tsplit_up_sign = '┴'.decode('utf-8')
-        left_sign = '╭'.decode('utf-8')
-        right_sign = '╮'.decode('utf-8')
-
         if node_len == 1:
             # Unary operators
-            edge_line = center_text(pipe_sign, box_widths[0], middle)
+            edge_line = center_text(PIPE_SIGN, box_widths[0], middle)
         elif node_len % 2:
             # n-ary operators (n is odd)
             edge_line = ''
 
             for i, child in enumerate(node):
                 if i > 0:
-                    edge_line += dash_sign
+                    edge_line += DASH_SIGN
 
                 if i < middle_node:
-                    marker = (left_sign if i == 0 else tsplit_dn_sign)
+                    marker = (LEFT_SIGN if i == 0 else TSPLIT_DN_SIGN)
                     edge_line += center_text(marker, box_widths[i],
-                                             middle=0, right=dash_sign)
+                                             middle=0, right=DASH_SIGN)
                 else:
                     if i == middle_node:
-                        marker = cross_sign
+                        marker = CROSS_SIGN
                         edge_line += center_text(marker, box_widths[i],
-                                                middle=0, right=dash_sign,
-                                                left=dash_sign)
+                                                middle=0, right=DASH_SIGN,
+                                                left=DASH_SIGN)
                     else:
                         if i == node_len - 1:
-                            marker = right_sign
+                            marker = RIGHT_SIGN
                         else:
-                            marker = tsplit_dn_sign
+                            marker = TSPLIT_DN_SIGN
 
                         edge_line += center_text(marker, box_widths[i],
-                                                 middle=0, left=dash_sign)
+                                                 middle=0, left=DASH_SIGN)
         else:
             # n-ary operators (n is even)
             edge_line = ''
@@ -162,24 +162,24 @@ def generate_graph(root, separator=' ', verbose=False):
             for i, child in enumerate(node):
                 if i > 0:
                     if i == middle_node:
-                        edge_line += tsplit_up_sign
+                        edge_line += TSPLIT_UP_SIGN
                     else:
-                        edge_line += dash_sign
+                        edge_line += DASH_SIGN
 
                 if i < middle_node:
-                    marker = (left_sign if i == 0 else tsplit_dn_sign)
+                    marker = (LEFT_SIGN if i == 0 else TSPLIT_DN_SIGN)
                     edge_line += center_text(marker, box_widths[i],
                                              middle=node_middle[child],
-                                             right=dash_sign)
+                                             right=DASH_SIGN)
                 else:
                     if i == node_len - 1:
-                        marker = right_sign
+                        marker = RIGHT_SIGN
                     else:
-                        marker = tsplit_dn_sign
+                        marker = TSPLIT_DN_SIGN
 
                     edge_line += center_text(marker, box_widths[i],
                                              middle=node_middle[child],
-                                             left=dash_sign)
+                                             left=DASH_SIGN)
 
         try:
             assert len(title_line) == len(edge_line)
@@ -215,10 +215,11 @@ def center_text(text, width, middle=0, left=' ', right=' '):
     │
     >>> center_text('+', 15, 11)
     '           +   '
-    >>> left = center_text('╭'.decode('utf-8'), 11, 8, right='─'.decode('utf-8'))
+    >>> sep = '─'.decode('utf-8')
+    >>> left = center_text('╭'.decode('utf-8'), 11, 8, right=sep)
     >>> len(left) == 11
     True
-    >>> right = center_text('╮'.decode('utf-8'), 3, 2, left='─'.decode('utf-8'))
+    >>> right = center_text('╮'.decode('utf-8'), 3, 2, left=sep)
     >>> len(right) == 3
     True
     >>> edge_line = left + '┴'.decode('utf-8') + right

line.py

 from node import Leaf
 
+
 def generate_line(root):
     """
     Print an expression tree in a single text line. Where needed, add