Make fnmatch be more PEP 8 compliant.

Partially closes issue 9356. Thanks to Brian Brazil for the patch.

Lib/fnmatch.py

@@ -9,20 +9,23 @@ expression.  They cache the compiled regular expressions for speed.
 The function translate(PATTERN) returns a regular expression
 corresponding to PATTERN.  (It does not compile it.)
 """
-
+import os
+import posixpath
 import re
 
 __all__ = ["filter", "fnmatch", "fnmatchcase", "purge", "translate"]
 
 _cache = {}  # Maps text patterns to compiled regexen.
 _cacheb = {}  # Ditto for bytes patterns.
-_MAXCACHE = 100 # Maximum size of caches
+_MAXCACHE = 100  # Maximum size of caches.
+
 
 def purge():
-    """Clear the pattern cache"""
+    """Clear the pattern cache."""
     _cache.clear()
     _cacheb.clear()
 
+
 def fnmatch(name, pat):
     """Test whether FILENAME matches PATTERN.
 
@@ -38,12 +41,11 @@ def fnmatch(name, pat):
     if the operating system requires it.
     If you don't want this, use fnmatchcase(FILENAME, PATTERN).
     """
-
-    import os
     name = os.path.normcase(name)
     pat = os.path.normcase(pat)
     return fnmatchcase(name, pat)
 
+
 def _compile_pattern(pat):
     cache = _cacheb if isinstance(pat, bytes) else _cache
     regex = cache.get(pat)
@@ -59,9 +61,9 @@ def _compile_pattern(pat):
         cache[pat] = regex = re.compile(res)
     return regex.match
 
+
 def filter(names, pat):
-    """Return the subset of the list NAMES that match PAT"""
-    import os,posixpath
+    """Return the subset of the list NAMES that match PAT."""
     result = []
     pat = os.path.normcase(pat)
     match = _compile_pattern(pat)
@@ -76,16 +78,17 @@ def filter(names, pat):
                 result.append(name)
     return result
 
+
 def fnmatchcase(name, pat):
     """Test whether FILENAME matches PATTERN, including case.
 
     This is a version of fnmatch() which doesn't case-normalize
     its arguments.
     """
-
     match = _compile_pattern(pat)
     return match(name) is not None
 
+
 def translate(pat):
     """Translate a shell PATTERN to a regular expression.