Fix columnize bug, where tab completion with very long filenames would crash Qt console

IPython/frontend/qt/console/console_widget.py

@@ -19,6 +19,7 @@
 from IPython.config.configurable import Configurable
 from IPython.frontend.qt.rich_text import HtmlExporter
 from IPython.frontend.qt.util import MetaQObjectHasTraits, get_font
+from IPython.utils.text import columnize
 from IPython.utils.traitlets import Bool, Enum, Int, Unicode
 from ansi_code_processor import QtAnsiCodeProcessor
 from completion_widget import CompletionWidget
@@ -1295,52 +1296,7 @@ def _format_as_columns(self, items, separator='  '):
         width = self._control.viewport().width()
         char_width = QtGui.QFontMetrics(self.font).width(' ')
         displaywidth = max(10, (width / char_width) - 1)
-
-        # Some degenerate cases.
-        size = len(items)
-        if size == 0: 
-            return '\n'
-        elif size == 1:
-            return '%s\n' % items[0]
-
-        # Try every row count from 1 upwards
-        array_index = lambda nrows, row, col: nrows*col + row
-        for nrows in range(1, size):
-            ncols = (size + nrows - 1) // nrows
-            colwidths = []
-            totwidth = -len(separator)
-            for col in range(ncols):
-                # Get max column width for this column
-                colwidth = 0
-                for row in range(nrows):
-                    i = array_index(nrows, row, col)
-                    if i >= size: break
-                    x = items[i]
-                    colwidth = max(colwidth, len(x))
-                colwidths.append(colwidth)
-                totwidth += colwidth + len(separator)
-                if totwidth > displaywidth: 
-                    break
-            if totwidth <= displaywidth: 
-                break
-
-        # The smallest number of rows computed and the max widths for each
-        # column has been obtained. Now we just have to format each of the rows.
-        string = ''
-        for row in range(nrows):
-            texts = []
-            for col in range(ncols):
-                i = row + nrows*col
-                if i >= size:
-                    texts.append('')
-                else:
-                    texts.append(items[i])
-            while texts and not texts[-1]:
-                del texts[-1]
-            for col in range(len(texts)):
-                texts[col] = texts[col].ljust(colwidths[col])
-            string += '%s\n' % separator.join(texts)
-        return string
+        return columnize(items, separator, displaywidth)
 
     def _get_block_plain_text(self, block):
         """ Given a QTextBlock, return its unformatted text.

IPython/utils/tests/test_text.py

@@ -0,0 +1,44 @@
+# encoding: utf-8
+"""Tests for IPython.utils.text"""
+
+#-----------------------------------------------------------------------------
+#  Copyright (C) 2011  The IPython Development Team
+#
+#  Distributed under the terms of the BSD License.  The full license is in
+#  the file COPYING, distributed as part of this software.
+#-----------------------------------------------------------------------------
+
+#-----------------------------------------------------------------------------
+# Imports
+#-----------------------------------------------------------------------------
+
+import os
+
+import nose.tools as nt
+
+from nose import with_setup
+
+from IPython.testing import decorators as dec
+from IPython.utils import text
+
+#-----------------------------------------------------------------------------
+# Globals
+#-----------------------------------------------------------------------------
+
+def test_columnize():
+    """Basic columnize tests."""
+    size = 5
+    items = [l*size for l in 'abc']
+    out = text.columnize(items, displaywidth=80)
+    nt.assert_equals(out, 'aaaaa  bbbbb  ccccc\n')
+    out = text.columnize(items, displaywidth=10)
+    nt.assert_equals(out, 'aaaaa  ccccc\nbbbbb\n')
+
+
+def test_columnize_long():
+    """Test columnize with inputs longer than the display window"""
+    text.columnize(['a'*81, 'b'*81], displaywidth=80)
+    size = 11
+    items = [l*size for l in 'abc']
+    out = text.columnize(items, displaywidth=size-1)
+    nt.assert_equals(out, '\n'.join(items+['']))

IPython/utils/text.py

@@ -611,3 +611,76 @@ def get_value(self, key, args, kwargs):
                 raise KeyError(key)
 
 
+def columnize(items, separator='  ', displaywidth=80):
+    """ Transform a list of strings into a single string with columns.
+
+    Parameters
+    ----------
+    items : sequence of strings
+        The strings to process.
+
+    separator : str, optional [default is two spaces]
+        The string that separates columns.
+
+    displaywidth : int, optional [default is 80]
+        Width of the display in number of characters.
+
+    Returns
+    -------
+    The formatted string.
+    """
+    # Note: this code is adapted from columnize 0.3.2.
+    # See http://code.google.com/p/pycolumnize/
+
+    # Some degenerate cases.
+    size = len(items)
+    if size == 0: 
+        return '\n'
+    elif size == 1:
+        return '%s\n' % items[0]
+
+    # Special case: if any item is longer than the maximum width, there's no
+    # point in triggering the logic below...
+    item_len = map(len, items) # save these, we can reuse them below
+    longest = max(item_len)
+    if longest >= displaywidth:
+        return '\n'.join(items+[''])
+
+    # Try every row count from 1 upwards
+    array_index = lambda nrows, row, col: nrows*col + row
+    for nrows in range(1, size):
+        ncols = (size + nrows - 1) // nrows
+        colwidths = []
+        totwidth = -len(separator)
+        for col in range(ncols):
+            # Get max column width for this column
+            colwidth = 0
+            for row in range(nrows):
+                i = array_index(nrows, row, col)
+                if i >= size: break
+                x, len_x = items[i], item_len[i]
+                colwidth = max(colwidth, len_x)
+            colwidths.append(colwidth)
+            totwidth += colwidth + len(separator)
+            if totwidth > displaywidth: 
+                break
+        if totwidth <= displaywidth: 
+            break
+
+    # The smallest number of rows computed and the max widths for each
+    # column has been obtained. Now we just have to format each of the rows.
+    string = ''
+    for row in range(nrows):
+        texts = []
+        for col in range(ncols):
+            i = row + nrows*col
+            if i >= size:
+                texts.append('')
+            else:
+                texts.append(items[i])
+        while texts and not texts[-1]:
+            del texts[-1]
+        for col in range(len(texts)):
+            texts[col] = texts[col].ljust(colwidths[col])
+        string += '%s\n' % separator.join(texts)
+    return string