updated based on comment from @takluyver

IPython/lib/display.py

@@ -1,301 +1,301
 """Various display related classes.
 
 Authors : MinRK, gregcaporaso, dannystaple
 """
 import urllib
 
 from os.path import exists, isfile, splitext, abspath, join, isdir
 from os import walk, sep
 
 
 class YouTubeVideo(object):
     """Class for embedding a YouTube Video in an IPython session, based on its video id.
 
     e.g. to embed the video on this page:
 
     http://www.youtube.com/watch?v=foo
 
     you would do:
 
     vid = YouTubeVideo("foo")
     display(vid)
     
     To start from 30 seconds:
     
     vid = YouTubeVideo("abc", start=30)
     display(vid)
     
     To calculate seconds from time as hours, minutes, seconds use:
     start=int(timedelta(hours=1, minutes=46, seconds=40).total_seconds())
 
     Other parameters can be provided as documented at 
     https://developers.google.com/youtube/player_parameters#parameter-subheader
     """
 
     def __init__(self, id, width=400, height=300, **kwargs):
         self.id = id
         self.width = width
         self.height = height
         self.params = kwargs
 
     def _repr_html_(self):
         """return YouTube embed iframe for this video id"""
         if self.params:
             params = "?" + urllib.urlencode(self.params)
         else:
             params = ""
         return """
             <iframe
                 width="%i"
                 height="%i"
                 src="http://www.youtube.com/embed/%s%s"
                 frameborder="0"
                 allowfullscreen
             ></iframe>
         """ % (self.width, self.height, self.id, params)
 
 class FileLink(object):
     """Class for embedding a local file link in an IPython session, based on path
 
     e.g. to embed a link that was generated in the IPython notebook as my/data.txt
 
     you would do:
 
     local_file = FileLink("my/data.txt")
     display(local_file)
     
     or in the HTML notebook, just
     
     FileLink("my/data.txt")
     """
     
     html_link_str = "<a href='%s' target='_blank'>%s</a>"
     
     def __init__(self,
                  path,
                  url_prefix='files/',
                  result_html_prefix='',
                  result_html_suffix='<br>'):
         """
             path : path to the file or directory that should be formatted
             directory_prefix : prefix to be prepended to all files to form a
              working link [default: 'files']
             result_html_prefix : text to append to beginning to link
              [default: none]
             result_html_suffix : text to append at the end of link
              [default: '<br>']
         """
         if isdir(path):
             raise ValueError,\
              ("Cannot display a directory using FileLink. "
               "Use FileLinks to display '%s'." % path)
         self.path = path
         self.url_prefix = url_prefix
         self.result_html_prefix = result_html_prefix
         self.result_html_suffix = result_html_suffix
     
     def _format_path(self):
         fp = ''.join([self.url_prefix,self.path])
         return ''.join([self.result_html_prefix,
                         self.html_link_str % (fp, self.path),
                         self.result_html_suffix])
         
     def _repr_html_(self):
         """return html link to file
         """
         if not exists(self.path):
             return ("Path (<tt>%s</tt>) doesn't exist. " 
                     "It may still be in the process of "
                     "being generated, or you may have the "
                     "incorrect path." % self.path)
         
         return self._format_path()
     
     def __repr__(self):
         """return absolute path to file
         """
         return abspath(self.path)
 
 class FileLinks(FileLink):
     """Class for embedding local file links in an IPython session, based on path
 
     e.g. to embed links to files that were generated in the IPython notebook under my/data
 
     you would do:
 
     local_files = FileLinks("my/data")
     display(local_files)
     
     or in the HTML notebook, just
     
     FileLinks("my/data")
     
     """
     def __init__(self,
                  path,
                  url_prefix='files/',
                  included_suffixes=None,
                  result_html_prefix='',
                  result_html_suffix='<br>',
                  notebook_display_formatter=None,
                  terminal_display_formatter=None):
         """
             included_suffixes : list of filename suffixes to include when
              formatting output [default: include all files]
              
             See the FileLink (baseclass of LocalDirectory) docstring for 
              information on additional parameters.
              
             notebook_display_formatter : func used to format links for display 
              in the notebook. See discussion of formatter function below.
             
             terminal_display_formatter : func used to format links for display 
              in the terminal. See discussion of formatter function below.
              
             
             Passing custom formatter functions
             ----------------------------------
              Formatter functions must be of the form:
               f(dirname, fnames, included_suffixes)
                dirname : the name of a directory (a string), 
                fnames :  a list of the files in that directory 
                included_suffixes : a list of the file suffixes that should be 
                                    included in the output (passing None means 
                                    to include all suffixes in the output in
                                    the built-in formatters)
                
                returns a list of lines that should will be print in the 
                notebook (if passing notebook_display_formatter) or the terminal
                (if passing terminal_display_formatter). This function is iterated 
                over for each directory in self.path. Default formatters are in 
                place, can be passed here to support alternative formatting.
             
         """
         if isfile(path):
             raise ValueError,\
              ("Cannot display a file using FileLinks. "
               "Use FileLink to display '%s'." % path)
         self.included_suffixes = included_suffixes
         # remove trailing slashs for more consistent output formatting
         path = path.rstrip('/')
         
         self.path = path
         self.url_prefix = url_prefix
         self.result_html_prefix = result_html_prefix
         self.result_html_suffix = result_html_suffix
         
         self.notebook_display_formatter = \
              notebook_display_formatter or self._get_notebook_display_formatter()
         self.terminal_display_formatter = \
              terminal_display_formatter or self._get_terminal_display_formatter()
     
     def _get_display_formatter(self,
                                dirname_output_format,
                                fname_output_format,
                                fp_format,
                                fp_cleaner=None):
         """ generate built-in formatter function
            
            this is used to define both the notebook and terminal built-in 
             formatters as they only differ by some wrapper text for each entry
         
            dirname_output_format: string to use for formatting directory 
             names, dirname will be substituted for a single "%s" which
             must appear in this string
            fname_output_format: string to use for formatting file names,
             if a single "%s" appears in the string, fname will be substituted
             if two "%s" appear in the string, the path to fname will be 
              substituted for the first and fname will be substituted for the
              second
            fp_format: string to use for formatting filepaths, must contain
             exactly two "%s" and the dirname will be subsituted for the first
             and fname will be substituted for the second
         """
         def f(dirname, fnames, included_suffixes=None):
             result = []
             # begin by figuring out which filenames, if any, 
             # are going to be displayed
             display_fnames = []
             for fname in fnames:
                 if (isfile(join(dirname,fname)) and
                        (included_suffixes == None or
                         splitext(fname)[1] in included_suffixes)):
                       display_fnames.append(fname)
         
             if len(display_fnames) == 0:
                 # if there are no filenames to display, don't print anything
                 # (not even the directory name)
                 pass
             else:
                 # otherwise print the formatted directory name followed by 
                 # the formatted filenames
                 dirname_output_line = dirname_output_format % dirname
                 result.append(dirname_output_line)
                 for fname in display_fnames:
                     fp = fp_format % (dirname,fname)
-                    if fp_cleaner != None:
+                    if fp_cleaner is not None:
                         fp = fp_cleaner(fp)
                     try:
                         # output can include both a filepath and a filename...
                         fname_output_line = fname_output_format % (fp, fname)
                     except TypeError:
                         # ... or just a single filepath
                         fname_output_line = fname_output_format % fname
                     result.append(fname_output_line)
             return result
         return f
 
     def _get_notebook_display_formatter(self,
                                         spacer="&nbsp;&nbsp;"):
         """ generate function to use for notebook formatting
         """
         dirname_output_format = \
          self.result_html_prefix + "%s/" + self.result_html_suffix
         fname_output_format = \
          self.result_html_prefix + spacer + self.html_link_str + self.result_html_suffix
         fp_format = self.url_prefix + '%s/%s'
         if sep == "\\":
             # Working on a platform where the path separator is "\", so 
             # must convert these to "/" for generating a URI
             def fp_cleaner(fp):
                 # Replace all occurences of backslash ("\") with a forward
                 # slash ("/") - this is necessary on windows when a path is
                 # provided as input, but we must link to a URI
                 return fp.replace('\\','/')
         else:
             fp_cleaner = None
         
         return self._get_display_formatter(dirname_output_format,
                                            fname_output_format,
                                            fp_format,
                                            fp_cleaner)
 
     def _get_terminal_display_formatter(self,
                                         spacer="  "):
         """ generate function to use for terminal formatting
         """
         dirname_output_format = "%s/"
         fname_output_format = spacer + "%s"
         fp_format = '%s/%s'
         
         return self._get_display_formatter(dirname_output_format,
                                            fname_output_format,
                                            fp_format)
     
     def _format_path(self):
         result_lines = []
         walked_dir = list(walk(self.path))
         walked_dir.sort()
         for dirname, subdirs, fnames in walked_dir:
             result_lines += self.notebook_display_formatter(dirname, fnames, self.included_suffixes)
         return '\n'.join(result_lines)
     
     def __repr__(self):
         """return newline-separated absolute paths
         """
         result_lines = []
         walked_dir = list(walk(self.path))
         walked_dir.sort()
         for dirname, subdirs, fnames in walked_dir:
             result_lines += self.terminal_display_formatter(dirname, fnames, self.included_suffixes)
         return '\n'.join(result_lines)