Refactor strip_email_quotes

Also removes long_substr, which fixes the licesing issue mentioned
in  #13039.

IPython/utils/tests/test_text.py

@@ -1,213 +1,200 b''
 # 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 math
 import random
 import sys
 
 import nose.tools as nt
 from pathlib import Path
 
 from IPython.utils import text
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 def test_columnize():
     """Basic columnize tests."""
     size = 5
     items = [l*size for l in 'abcd']
 
     out = text.columnize(items, displaywidth=80)
     nt.assert_equal(out, 'aaaaa  bbbbb  ccccc  ddddd\n')
     out = text.columnize(items, displaywidth=25)
     nt.assert_equal(out, 'aaaaa  ccccc\nbbbbb  ddddd\n')
     out = text.columnize(items, displaywidth=12)
     nt.assert_equal(out, 'aaaaa  ccccc\nbbbbb  ddddd\n')
     out = text.columnize(items, displaywidth=10)
     nt.assert_equal(out, 'aaaaa\nbbbbb\nccccc\nddddd\n')
 
     out = text.columnize(items, row_first=True, displaywidth=80)
     nt.assert_equal(out, 'aaaaa  bbbbb  ccccc  ddddd\n')
     out = text.columnize(items, row_first=True, displaywidth=25)
     nt.assert_equal(out, 'aaaaa  bbbbb\nccccc  ddddd\n')
     out = text.columnize(items, row_first=True, displaywidth=12)
     nt.assert_equal(out, 'aaaaa  bbbbb\nccccc  ddddd\n')
     out = text.columnize(items, row_first=True, displaywidth=10)
     nt.assert_equal(out, 'aaaaa\nbbbbb\nccccc\nddddd\n')
 
     out = text.columnize(items, displaywidth=40, spread=True)
     nt.assert_equal(out, 'aaaaa      bbbbb      ccccc      ddddd\n')
     out = text.columnize(items, displaywidth=20, spread=True)
     nt.assert_equal(out, 'aaaaa          ccccc\nbbbbb          ddddd\n')
     out = text.columnize(items, displaywidth=12, spread=True)
     nt.assert_equal(out, 'aaaaa  ccccc\nbbbbb  ddddd\n')
     out = text.columnize(items, displaywidth=10, spread=True)
     nt.assert_equal(out, 'aaaaa\nbbbbb\nccccc\nddddd\n')
 
 
 def test_columnize_random():
     """Test with random input to hopefully catch edge case """
     for row_first in [True, False]:
         for nitems in [random.randint(2,70) for i in range(2,20)]:
             displaywidth = random.randint(20,200)
             rand_len = [random.randint(2,displaywidth) for i in range(nitems)]
             items = ['x'*l for l in rand_len]
             out = text.columnize(items, row_first=row_first, displaywidth=displaywidth)
             longer_line = max([len(x) for x in out.split('\n')])
             longer_element = max(rand_len)
             if longer_line > displaywidth:
                 print("Columnize displayed something lager than displaywidth : %s " % longer_line)
                 print("longer element : %s " % longer_element)
                 print("displaywidth : %s " % displaywidth)
                 print("number of element : %s " % nitems)
                 print("size of each element :\n %s" % rand_len)
                 assert False, "row_first={0}".format(row_first)
 
 def test_columnize_medium():
     """Test with inputs than shouldn't be wider than 80"""
     size = 40
     items = [l*size for l in 'abc']
     for row_first in [True, False]:
         out = text.columnize(items, row_first=row_first, displaywidth=80)
         nt.assert_equal(out, '\n'.join(items+['']), "row_first={0}".format(row_first))
 
 def test_columnize_long():
     """Test columnize with inputs longer than the display window"""
     size = 11
     items = [l*size for l in 'abc']
     for row_first in [True, False]:
         out = text.columnize(items, row_first=row_first, displaywidth=size-1)
         nt.assert_equal(out, '\n'.join(items+['']), "row_first={0}".format(row_first))
 
 def eval_formatter_check(f):
     ns = dict(n=12, pi=math.pi, stuff='hello there', os=os, u=u"café", b="café")
     s = f.format("{n} {n//4} {stuff.split()[0]}", **ns)
     nt.assert_equal(s, "12 3 hello")
     s = f.format(' '.join(['{n//%i}'%i for i in range(1,8)]), **ns)
     nt.assert_equal(s, "12 6 4 3 2 2 1")
     s = f.format('{[n//i for i in range(1,8)]}', **ns)
     nt.assert_equal(s, "[12, 6, 4, 3, 2, 2, 1]")
     s = f.format("{stuff!s}", **ns)
     nt.assert_equal(s, ns['stuff'])
     s = f.format("{stuff!r}", **ns)
     nt.assert_equal(s, repr(ns['stuff']))
     
     # Check with unicode:
     s = f.format("{u}", **ns)
     nt.assert_equal(s, ns['u'])
     # This decodes in a platform dependent manner, but it shouldn't error out
     s = f.format("{b}", **ns)
         
     nt.assert_raises(NameError, f.format, '{dne}', **ns)
 
 def eval_formatter_slicing_check(f):
     ns = dict(n=12, pi=math.pi, stuff='hello there', os=os)
     s = f.format(" {stuff.split()[:]} ", **ns)
     nt.assert_equal(s, " ['hello', 'there'] ")
     s = f.format(" {stuff.split()[::-1]} ", **ns)
     nt.assert_equal(s, " ['there', 'hello'] ")
     s = f.format("{stuff[::2]}", **ns)
     nt.assert_equal(s, ns['stuff'][::2])
     
     nt.assert_raises(SyntaxError, f.format, "{n:x}", **ns)
 
 def eval_formatter_no_slicing_check(f):
     ns = dict(n=12, pi=math.pi, stuff='hello there', os=os)
     
     s = f.format('{n:x} {pi**2:+f}', **ns)
     nt.assert_equal(s, "c +9.869604")
     
     s = f.format('{stuff[slice(1,4)]}', **ns)
     nt.assert_equal(s, 'ell')
 
     s = f.format("{a[:]}", a=[1, 2])
     nt.assert_equal(s, "[1, 2]")
 
 def test_eval_formatter():
     f = text.EvalFormatter()
     eval_formatter_check(f)
     eval_formatter_no_slicing_check(f)
 
 def test_full_eval_formatter():
     f = text.FullEvalFormatter()
     eval_formatter_check(f)
     eval_formatter_slicing_check(f)
 
 def test_dollar_formatter():
     f = text.DollarFormatter()
     eval_formatter_check(f)
     eval_formatter_slicing_check(f)
     
     ns = dict(n=12, pi=math.pi, stuff='hello there', os=os)
     s = f.format("$n", **ns)
     nt.assert_equal(s, "12")
     s = f.format("$n.real", **ns)
     nt.assert_equal(s, "12")
     s = f.format("$n/{stuff[:5]}", **ns)
     nt.assert_equal(s, "12/hello")
     s = f.format("$n $$HOME", **ns)
     nt.assert_equal(s, "12 $HOME")
     s = f.format("${foo}", foo="HOME")
     nt.assert_equal(s, "$HOME")
 
 
-def test_long_substr():
-    data = ['hi']
-    nt.assert_equal(text.long_substr(data), 'hi')
-
-
-def test_long_substr2():
-    data = ['abc', 'abd', 'abf', 'ab']
-    nt.assert_equal(text.long_substr(data), 'ab')
-
-def test_long_substr_empty():
-    data = []
-    nt.assert_equal(text.long_substr(data), '')
-
 def test_strip_email():
     src = """\
         >> >>> def f(x):
         >> ...   return x+1
         >> ... 
         >> >>> zz = f(2.5)"""
     cln = """\
 >>> def f(x):
 ...   return x+1
 ... 
 >>> zz = f(2.5)"""
     nt.assert_equal(text.strip_email_quotes(src), cln)
 
 
 def test_strip_email2():
     src = '> > > list()'
     cln = 'list()'
     nt.assert_equal(text.strip_email_quotes(src), cln)
 
 def test_LSString():
     lss = text.LSString("abc\ndef")
     nt.assert_equal(lss.l, ['abc', 'def'])
     nt.assert_equal(lss.s, 'abc def')
     lss = text.LSString(os.getcwd())
     nt.assert_is_instance(lss.p[0], Path)
 
 def test_SList():
     sl = text.SList(['a 11', 'b 1', 'a 2'])
     nt.assert_equal(sl.n, 'a 11\nb 1\na 2')
     nt.assert_equal(sl.s, 'a 11 b 1 a 2')
     nt.assert_equal(sl.grep(lambda x: x.startswith('a')), text.SList(['a 11', 'a 2']))
     nt.assert_equal(sl.fields(0), text.SList(['a', 'b', 'a']))
     nt.assert_equal(sl.sort(field=1, nums=True), text.SList(['b 1', 'a 2', 'a 11']))

IPython/utils/text.py

@@ -1,761 +1,749 b''
 # encoding: utf-8
 """
 Utilities for working with strings and text.
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.utils.text
    :parts: 3
 """
 
 import os
 import re
+import string
 import sys
 import textwrap
 from string import Formatter
 from pathlib import Path
 
 
 # datetime.strftime date format for ipython
 if sys.platform == 'win32':
     date_format = "%B %d, %Y"
 else:
     date_format = "%B %-d, %Y"
 
 class LSString(str):
     """String derivative with a special access attributes.
 
     These are normal strings, but with the special attributes:
 
         .l (or .list) : value as list (split on newlines).
         .n (or .nlstr): original value (the string itself).
         .s (or .spstr): value as whitespace-separated string.
         .p (or .paths): list of path objects (requires path.py package)
 
     Any values which require transformations are computed only once and
     cached.
 
     Such strings are very useful to efficiently interact with the shell, which
     typically only understands whitespace-separated options for commands."""
 
     def get_list(self):
         try:
             return self.__list
         except AttributeError:
             self.__list = self.split('\n')
             return self.__list
 
     l = list = property(get_list)
 
     def get_spstr(self):
         try:
             return self.__spstr
         except AttributeError:
             self.__spstr = self.replace('\n',' ')
             return self.__spstr
 
     s = spstr = property(get_spstr)
 
     def get_nlstr(self):
         return self
 
     n = nlstr = property(get_nlstr)
 
     def get_paths(self):
         try:
             return self.__paths
         except AttributeError:
             self.__paths = [Path(p) for p in self.split('\n') if os.path.exists(p)]
             return self.__paths
 
     p = paths = property(get_paths)
 
 # FIXME: We need to reimplement type specific displayhook and then add this
 # back as a custom printer. This should also be moved outside utils into the
 # core.
 
 # def print_lsstring(arg):
 #     """ Prettier (non-repr-like) and more informative printer for LSString """
 #     print "LSString (.p, .n, .l, .s available). Value:"
 #     print arg
 #
 #
 # print_lsstring = result_display.register(LSString)(print_lsstring)
 
 
 class SList(list):
     """List derivative with a special access attributes.
 
     These are normal lists, but with the special attributes:
 
     * .l (or .list) : value as list (the list itself).
     * .n (or .nlstr): value as a string, joined on newlines.
     * .s (or .spstr): value as a string, joined on spaces.
     * .p (or .paths): list of path objects (requires path.py package)
 
     Any values which require transformations are computed only once and
     cached."""
 
     def get_list(self):
         return self
 
     l = list = property(get_list)
 
     def get_spstr(self):
         try:
             return self.__spstr
         except AttributeError:
             self.__spstr = ' '.join(self)
             return self.__spstr
 
     s = spstr = property(get_spstr)
 
     def get_nlstr(self):
         try:
             return self.__nlstr
         except AttributeError:
             self.__nlstr = '\n'.join(self)
             return self.__nlstr
 
     n = nlstr = property(get_nlstr)
 
     def get_paths(self):
         try:
             return self.__paths
         except AttributeError:
             self.__paths = [Path(p) for p in self if os.path.exists(p)]
             return self.__paths
 
     p = paths = property(get_paths)
 
     def grep(self, pattern, prune = False, field = None):
         """ Return all strings matching 'pattern' (a regex or callable)
 
         This is case-insensitive. If prune is true, return all items
         NOT matching the pattern.
 
         If field is specified, the match must occur in the specified
         whitespace-separated field.
 
         Examples::
 
             a.grep( lambda x: x.startswith('C') )
             a.grep('Cha.*log', prune=1)
             a.grep('chm', field=-1)
         """
 
         def match_target(s):
             if field is None:
                 return s
             parts = s.split()
             try:
                 tgt = parts[field]
                 return tgt
             except IndexError:
                 return ""
 
         if isinstance(pattern, str):
             pred = lambda x : re.search(pattern, x, re.IGNORECASE)
         else:
             pred = pattern
         if not prune:
             return SList([el for el in self if pred(match_target(el))])
         else:
             return SList([el for el in self if not pred(match_target(el))])
 
     def fields(self, *fields):
         """ Collect whitespace-separated fields from string list
 
         Allows quick awk-like usage of string lists.
 
         Example data (in var a, created by 'a = !ls -l')::
 
             -rwxrwxrwx  1 ville None      18 Dec 14  2006 ChangeLog
             drwxrwxrwx+ 6 ville None       0 Oct 24 18:05 IPython
 
         * ``a.fields(0)`` is ``['-rwxrwxrwx', 'drwxrwxrwx+']``
         * ``a.fields(1,0)`` is ``['1 -rwxrwxrwx', '6 drwxrwxrwx+']``
           (note the joining by space).
         * ``a.fields(-1)`` is ``['ChangeLog', 'IPython']``
 
         IndexErrors are ignored.
 
         Without args, fields() just split()'s the strings.
         """
         if len(fields) == 0:
             return [el.split() for el in self]
 
         res = SList()
         for el in [f.split() for f in self]:
             lineparts = []
 
             for fd in fields:
                 try:
                     lineparts.append(el[fd])
                 except IndexError:
                     pass
             if lineparts:
                 res.append(" ".join(lineparts))
 
         return res
 
     def sort(self,field= None,  nums = False):
         """ sort by specified fields (see fields())
 
         Example::
 
             a.sort(1, nums = True)
 
         Sorts a by second field, in numerical order (so that 21 > 3)
 
         """
 
         #decorate, sort, undecorate
         if field is not None:
             dsu = [[SList([line]).fields(field),  line] for line in self]
         else:
             dsu = [[line,  line] for line in self]
         if nums:
             for i in range(len(dsu)):
                 numstr = "".join([ch for ch in dsu[i][0] if ch.isdigit()])
                 try:
                     n = int(numstr)
                 except ValueError:
                     n = 0
                 dsu[i][0] = n
 
 
         dsu.sort()
         return SList([t[1] for t in dsu])
 
 
 # FIXME: We need to reimplement type specific displayhook and then add this
 # back as a custom printer. This should also be moved outside utils into the
 # core.
 
 # def print_slist(arg):
 #     """ Prettier (non-repr-like) and more informative printer for SList """
 #     print "SList (.p, .n, .l, .s, .grep(), .fields(), sort() available):"
 #     if hasattr(arg,  'hideonce') and arg.hideonce:
 #         arg.hideonce = False
 #         return
 #
 #     nlprint(arg)   # This was a nested list printer, now removed.
 #
 # print_slist = result_display.register(SList)(print_slist)
 
 
 def indent(instr,nspaces=4, ntabs=0, flatten=False):
     """Indent a string a given number of spaces or tabstops.
 
     indent(str,nspaces=4,ntabs=0) -> indent str by ntabs+nspaces.
 
     Parameters
     ----------
     instr : basestring
         The string to be indented.
     nspaces : int (default: 4)
         The number of spaces to be indented.
     ntabs : int (default: 0)
         The number of tabs to be indented.
     flatten : bool (default: False)
         Whether to scrub existing indentation.  If True, all lines will be
         aligned to the same indentation.  If False, existing indentation will
         be strictly increased.
 
     Returns
     -------
     str|unicode : string indented by ntabs and nspaces.
 
     """
     if instr is None:
         return
     ind = '\t'*ntabs+' '*nspaces
     if flatten:
         pat = re.compile(r'^\s*', re.MULTILINE)
     else:
         pat = re.compile(r'^', re.MULTILINE)
     outstr = re.sub(pat, ind, instr)
     if outstr.endswith(os.linesep+ind):
         return outstr[:-len(ind)]
     else:
         return outstr
 
 
 def list_strings(arg):
     """Always return a list of strings, given a string or list of strings
     as input.
 
     Examples
     --------
     ::
 
         In [7]: list_strings('A single string')
         Out[7]: ['A single string']
 
         In [8]: list_strings(['A single string in a list'])
         Out[8]: ['A single string in a list']
 
         In [9]: list_strings(['A','list','of','strings'])
         Out[9]: ['A', 'list', 'of', 'strings']
     """
 
     if isinstance(arg, str):
         return [arg]
     else:
         return arg
 
 
 def marquee(txt='',width=78,mark='*'):
     """Return the input string centered in a 'marquee'.
 
     Examples
     --------
     ::
 
         In [16]: marquee('A test',40)
         Out[16]: '**************** A test ****************'
 
         In [17]: marquee('A test',40,'-')
         Out[17]: '---------------- A test ----------------'
 
         In [18]: marquee('A test',40,' ')
         Out[18]: '                 A test                 '
 
     """
     if not txt:
         return (mark*width)[:width]
     nmark = (width-len(txt)-2)//len(mark)//2
     if nmark < 0: nmark =0
     marks = mark*nmark
     return '%s %s %s' % (marks,txt,marks)
 
 
 ini_spaces_re = re.compile(r'^(\s+)')
 
 def num_ini_spaces(strng):
     """Return the number of initial spaces in a string"""
 
     ini_spaces = ini_spaces_re.match(strng)
     if ini_spaces:
         return ini_spaces.end()
     else:
         return 0
 
 
 def format_screen(strng):
     """Format a string for screen printing.
 
     This removes some latex-type format codes."""
     # Paragraph continue
     par_re = re.compile(r'\\$',re.MULTILINE)
     strng = par_re.sub('',strng)
     return strng
 
 
 def dedent(text):
     """Equivalent of textwrap.dedent that ignores unindented first line.
 
     This means it will still dedent strings like:
     '''foo
     is a bar
     '''
 
     For use in wrap_paragraphs.
     """
 
     if text.startswith('\n'):
         # text starts with blank line, don't ignore the first line
         return textwrap.dedent(text)
 
     # split first line
     splits = text.split('\n',1)
     if len(splits) == 1:
         # only one line
         return textwrap.dedent(text)
 
     first, rest = splits
     # dedent everything but the first line
     rest = textwrap.dedent(rest)
     return '\n'.join([first, rest])
 
 
 def wrap_paragraphs(text, ncols=80):
     """Wrap multiple paragraphs to fit a specified width.
 
     This is equivalent to textwrap.wrap, but with support for multiple
     paragraphs, as separated by empty lines.
 
     Returns
     -------
     list of complete paragraphs, wrapped to fill `ncols` columns.
     """
     paragraph_re = re.compile(r'\n(\s*\n)+', re.MULTILINE)
     text = dedent(text).strip()
     paragraphs = paragraph_re.split(text)[::2] # every other entry is space
     out_ps = []
     indent_re = re.compile(r'\n\s+', re.MULTILINE)
     for p in paragraphs:
         # presume indentation that survives dedent is meaningful formatting,
         # so don't fill unless text is flush.
         if indent_re.search(p) is None:
             # wrap paragraph
             p = textwrap.fill(p, ncols)
         out_ps.append(p)
     return out_ps
 
 
-def long_substr(data):
-    """Return the longest common substring in a list of strings.
-
-    Credit: http://stackoverflow.com/questions/2892931/longest-common-substring-from-more-than-two-strings-python
-    """
-    substr = ''
-    if len(data) > 1 and len(data[0]) > 0:
-        for i in range(len(data[0])):
-            for j in range(len(data[0])-i+1):
-                if j > len(substr) and all(data[0][i:i+j] in x for x in data):
-                    substr = data[0][i:i+j]
-    elif len(data) == 1:
-        substr = data[0]
-    return substr
-
-
 def strip_email_quotes(text):
     """Strip leading email quotation characters ('>').
 
     Removes any combination of leading '>' interspersed with whitespace that
     appears *identically* in all lines of the input text.
 
     Parameters
     ----------
     text : str
 
     Examples
     --------
 
     Simple uses::
 
         In [2]: strip_email_quotes('> > text')
         Out[2]: 'text'
 
         In [3]: strip_email_quotes('> > text\\n> > more')
         Out[3]: 'text\\nmore'
 
     Note how only the common prefix that appears in all lines is stripped::
 
         In [4]: strip_email_quotes('> > text\\n> > more\\n> more...')
         Out[4]: '> text\\n> more\\nmore...'
 
-    So if any line has no quote marks ('>') , then none are stripped from any
+    So if any line has no quote marks ('>'), then none are stripped from any
     of them ::
-    
+
         In [5]: strip_email_quotes('> > text\\n> > more\\nlast different')
         Out[5]: '> > text\\n> > more\\nlast different'
     """
     lines = text.splitlines()
-    matches = set()
-    for line in lines:
-        prefix = re.match(r'^(\s*>[ >]*)', line)
-        if prefix:
-            matches.add(prefix.group(1))
+    strip_len = 0
+
+    for characters in zip(*lines):
+        # Check if all characters in this position are the same
+        if len(set(characters)) > 1:
+            break
+        prefix_char = characters[0][0]
+
+        if prefix_char in string.whitespace or prefix_char == ">":
+            strip_len += 1
         else:
             break
-    else:
-        prefix = long_substr(list(matches))
-        if prefix:
-            strip = len(prefix)
-            text = '\n'.join([ ln[strip:] for ln in lines])
+
+    text = "\n".join([ln[strip_len:] for ln in lines])
     return text
 
+
 def strip_ansi(source):
     """
     Remove ansi escape codes from text.
 
     Parameters
     ----------
     source : str
         Source to remove the ansi from
     """
     return re.sub(r'\033\[(\d|;)+?m', '', source)
 
 
 class EvalFormatter(Formatter):
     """A String Formatter that allows evaluation of simple expressions.
     
     Note that this version interprets a : as specifying a format string (as per
     standard string formatting), so if slicing is required, you must explicitly
     create a slice.
     
     This is to be used in templating cases, such as the parallel batch
     script templates, where simple arithmetic on arguments is useful.
 
     Examples
     --------
     ::
 
         In [1]: f = EvalFormatter()
         In [2]: f.format('{n//4}', n=8)
         Out[2]: '2'
 
         In [3]: f.format("{greeting[slice(2,4)]}", greeting="Hello")
         Out[3]: 'll'
     """
     def get_field(self, name, args, kwargs):
         v = eval(name, kwargs)
         return v, name
 
 #XXX: As of Python 3.4, the format string parsing no longer splits on a colon
 # inside [], so EvalFormatter can handle slicing. Once we only support 3.4 and
 # above, it should be possible to remove FullEvalFormatter.
 
 class FullEvalFormatter(Formatter):
     """A String Formatter that allows evaluation of simple expressions.
     
     Any time a format key is not found in the kwargs,
     it will be tried as an expression in the kwargs namespace.
     
     Note that this version allows slicing using [1:2], so you cannot specify
     a format string. Use :class:`EvalFormatter` to permit format strings.
     
     Examples
     --------
     ::
 
         In [1]: f = FullEvalFormatter()
         In [2]: f.format('{n//4}', n=8)
         Out[2]: '2'
 
         In [3]: f.format('{list(range(5))[2:4]}')
         Out[3]: '[2, 3]'
 
         In [4]: f.format('{3*2}')
         Out[4]: '6'
     """
     # copied from Formatter._vformat with minor changes to allow eval
     # and replace the format_spec code with slicing
     def vformat(self, format_string:str, args, kwargs)->str:
         result = []
         for literal_text, field_name, format_spec, conversion in \
                 self.parse(format_string):
 
             # output the literal text
             if literal_text:
                 result.append(literal_text)
 
             # if there's a field, output it
             if field_name is not None:
                 # this is some markup, find the object and do
                 # the formatting
 
                 if format_spec:
                     # override format spec, to allow slicing:
                     field_name = ':'.join([field_name, format_spec])
 
                 # eval the contents of the field for the object
                 # to be formatted
                 obj = eval(field_name, kwargs)
 
                 # do any conversion on the resulting object
                 obj = self.convert_field(obj, conversion)
 
                 # format the object and append to the result
                 result.append(self.format_field(obj, ''))
 
         return ''.join(result)
 
 
 class DollarFormatter(FullEvalFormatter):
     """Formatter allowing Itpl style $foo replacement, for names and attribute
     access only. Standard {foo} replacement also works, and allows full
     evaluation of its arguments.
 
     Examples
     --------
     ::
 
         In [1]: f = DollarFormatter()
         In [2]: f.format('{n//4}', n=8)
         Out[2]: '2'
 
         In [3]: f.format('23 * 76 is $result', result=23*76)
         Out[3]: '23 * 76 is 1748'
 
         In [4]: f.format('$a or {b}', a=1, b=2)
         Out[4]: '1 or 2'
     """
     _dollar_pattern_ignore_single_quote = re.compile(r"(.*?)\$(\$?[\w\.]+)(?=([^']*'[^']*')*[^']*$)")
     def parse(self, fmt_string):
         for literal_txt, field_name, format_spec, conversion \
                     in Formatter.parse(self, fmt_string):
             
             # Find $foo patterns in the literal text.
             continue_from = 0
             txt = ""
             for m in self._dollar_pattern_ignore_single_quote.finditer(literal_txt):
                 new_txt, new_field = m.group(1,2)
                 # $$foo --> $foo
                 if new_field.startswith("$"):
                     txt += new_txt + new_field
                 else:
                     yield (txt + new_txt, new_field, "", None)
                     txt = ""
                 continue_from = m.end()
             
             # Re-yield the {foo} style pattern
             yield (txt + literal_txt[continue_from:], field_name, format_spec, conversion)
 
 #-----------------------------------------------------------------------------
 # Utils to columnize a list of string
 #-----------------------------------------------------------------------------
 
 def _col_chunks(l, max_rows, row_first=False):
     """Yield successive max_rows-sized column chunks from l."""
     if row_first:
         ncols = (len(l) // max_rows) + (len(l) % max_rows > 0)
         for i in range(ncols):
             yield [l[j] for j in range(i, len(l), ncols)]
     else:
         for i in range(0, len(l), max_rows):
             yield l[i:(i + max_rows)]
 
 
 def _find_optimal(rlist, row_first=False, separator_size=2, displaywidth=80):
     """Calculate optimal info to columnize a list of string"""
     for max_rows in range(1, len(rlist) + 1):
         col_widths = list(map(max, _col_chunks(rlist, max_rows, row_first)))
         sumlength = sum(col_widths)
         ncols = len(col_widths)
         if sumlength + separator_size * (ncols - 1) <= displaywidth:
             break
     return {'num_columns': ncols,
             'optimal_separator_width': (displaywidth - sumlength) // (ncols - 1) if (ncols - 1) else 0,
             'max_rows': max_rows,
             'column_widths': col_widths
             }
 
 
 def _get_or_default(mylist, i, default=None):
     """return list item number, or default if don't exist"""
     if i >= len(mylist):
         return default
     else :
         return mylist[i]
 
 
 def compute_item_matrix(items, row_first=False, empty=None, *args, **kwargs) :
     """Returns a nested list, and info to columnize items
 
     Parameters
     ----------
     items
         list of strings to columize
     row_first : (default False)
         Whether to compute columns for a row-first matrix instead of
         column-first (default).
     empty : (default None)
         default value to fill list if needed
     separator_size : int (default=2)
         How much characters will be used as a separation between each columns.
     displaywidth : int (default=80)
         The width of the area onto which the columns should enter
 
     Returns
     -------
     strings_matrix
         nested list of string, the outer most list contains as many list as
         rows, the innermost lists have each as many element as columns. If the
         total number of elements in `items` does not equal the product of
         rows*columns, the last element of some lists are filled with `None`.
     dict_info
         some info to make columnize easier:
 
         num_columns
           number of columns
         max_rows
           maximum number of rows (final number may be less)
         column_widths
           list of with of each columns
         optimal_separator_width
           best separator width between columns
 
     Examples
     --------
     ::
 
         In [1]: l = ['aaa','b','cc','d','eeeee','f','g','h','i','j','k','l']
         In [2]: list, info = compute_item_matrix(l, displaywidth=12)
         In [3]: list
         Out[3]: [['aaa', 'f', 'k'], ['b', 'g', 'l'], ['cc', 'h', None], ['d', 'i', None], ['eeeee', 'j', None]]
         In [4]: ideal = {'num_columns': 3, 'column_widths': [5, 1, 1], 'optimal_separator_width': 2, 'max_rows': 5}
         In [5]: all((info[k] == ideal[k] for k in ideal.keys()))
         Out[5]: True
     """
     info = _find_optimal(list(map(len, items)), row_first, *args, **kwargs)
     nrow, ncol = info['max_rows'], info['num_columns']
     if row_first:
         return ([[_get_or_default(items, r * ncol + c, default=empty) for c in range(ncol)] for r in range(nrow)], info)
     else:
         return ([[_get_or_default(items, c * nrow + r, default=empty) for c in range(ncol)] for r in range(nrow)], info)
 
 
 def columnize(items, row_first=False, separator='  ', displaywidth=80, spread=False):
     """ Transform a list of strings into a single string with columns.
 
     Parameters
     ----------
     items : sequence of strings
         The strings to process.
     row_first : (default False)
         Whether to compute columns for a row-first matrix instead of
         column-first (default).
     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.
     """
     if not items:
         return '\n'
     matrix, info = compute_item_matrix(items, row_first=row_first, separator_size=len(separator), displaywidth=displaywidth)
     if spread:
         separator = separator.ljust(int(info['optimal_separator_width']))
     fmatrix = [filter(None, x) for x in matrix]
     sjoin = lambda x : separator.join([ y.ljust(w, ' ') for y, w in zip(x, info['column_widths'])])
     return '\n'.join(map(sjoin, fmatrix))+'\n'
 
 
 def get_text_list(list_, last_sep=' and ', sep=", ", wrap_item_with=""):
     """
     Return a string with a natural enumeration of items
 
     >>> get_text_list(['a', 'b', 'c', 'd'])
     'a, b, c and d'
     >>> get_text_list(['a', 'b', 'c'], ' or ')
     'a, b or c'
     >>> get_text_list(['a', 'b', 'c'], ', ')
     'a, b, c'
     >>> get_text_list(['a', 'b'], ' or ')
     'a or b'
     >>> get_text_list(['a'])
     'a'
     >>> get_text_list([])
     ''
     >>> get_text_list(['a', 'b'], wrap_item_with="`")
     '`a` and `b`'
     >>> get_text_list(['a', 'b', 'c', 'd'], " = ", sep=" + ")
     'a + b + c = d'
     """
     if len(list_) == 0:
         return ''
     if wrap_item_with:
         list_ = ['%s%s%s' % (wrap_item_with, item, wrap_item_with) for
                  item in list_]
     if len(list_) == 1:
         return list_[0]
     return '%s%s%s' % (
         sep.join(i for i in list_[:-1]),
         last_sep, list_[-1])