* code to detect python version in util.py

  (py25, py26, py27)
* call this in __init__.py (deciding whether to import align, which requires 2.6+)
* call this in corpus/reader/util.py (deciding whether to use followlinks flag)

nltk/__init__.py

@@ -113,8 +113,7 @@ from util import *
 from yamltags import *
 
 # Modules that require Python 2.6
-from sys import version_info as vi
-if vi[0] == 2 and vi[1] >= 6:
+if py26() or py27():
     from align import *
 
 # don't import contents into top-level namespace:

nltk/corpus/reader/util.py

@@ -24,7 +24,7 @@ from nltk.internals import slice_bounds
 from nltk.data import PathPointer, FileSystemPathPointer, ZipFilePathPointer
 from nltk.data import SeekableUnicodeStreamReader
 from nltk.sourcedstring import SourcedStringStream
-from nltk.util import AbstractLazySequence, LazySubsequence, LazyConcatenation
+from nltk.util import AbstractLazySequence, LazySubsequence, LazyConcatenation, py25
 
 ######################################################################
 #{ Corpus View
@@ -760,7 +760,11 @@ def find_corpus_fileids(root, regexp):
     # or symlinked) subdirectories, and match paths against the regexp.
     elif isinstance(root, FileSystemPathPointer):
         items = []
-        for dirname, subdirs, fileids in os.walk(root.path, followlinks=True):
+        # workaround for py25 which doesn't support followlinks
+        kwargs = {}
+        if not py25():
+            kwargs = {'followlinks': True}
+        for dirname, subdirs, fileids in os.walk(root.path, **kwargs):
             prefix = ''.join('%s/' % p for p in _path_from(root.path, dirname))
             items += [prefix+fileid for fileid in fileids
                       if re.match(regexp, prefix+fileid)]

nltk/util.py

@@ -16,6 +16,7 @@ import os
 from itertools import islice, chain
 from pprint import pprint
 from collections import defaultdict, deque
+from sys import version_info
 
 from nltk.internals import slice_bounds
 
@@ -108,6 +109,18 @@ def tokenwrap(tokens, separator=" ", width=70):
 
 
 ##########################################################################
+# Python version
+##########################################################################
+
+def py25():
+    return version_info[0] == 2 and version_info[1] == 5
+def py26():
+    return version_info[0] == 2 and version_info[1] == 6
+def py27():
+    return version_info[0] == 2 and version_info[1] == 7
+
+
+##########################################################################
 # Indexing
 ##########################################################################