RF: Indexed_gzip import test performed once at top of openers.py. Additional

lock protection in ArrayProxy, on call to volumeutils.array_from_file.

Author: pauldmccarthy

nibabel/arrayproxy.py

@@ -34,7 +34,7 @@
 from .volumeutils import array_from_file, apply_read_scaling
 from .fileslice import fileslice
 from .keywordonly import kw_only_meth
-from .openers import ImageOpener
+from .openers import ImageOpener, HAVE_INDEXED_GZIP
 
 
 class ArrayProxy(object):
@@ -195,13 +195,7 @@ def _should_keep_file_open(self, file_like, keep_file_open):
             return bool(keep_file_open)
         # Otherwise, if file_like is gzipped, and we have_indexed_gzip, we set
         # keep_file_open to True, else we set it to False
-        try:
-            import indexed_gzip
-            have_indexed_gzip = True
-        except ImportError:
-            have_indexed_gzip = False
-
-        return have_indexed_gzip and file_like.endswith('gz')
+        return HAVE_INDEXED_GZIP and file_like.endswith('gz')
 
     @property
     @deprecate_with_version('ArrayProxy.header deprecated', '2.2', '3.0')
@@ -259,7 +253,7 @@ def get_unscaled(self):
 
         This is an optional part of the proxy API
         """
-        with self._get_fileobj() as fileobj:
+        with self._get_fileobj() as fileobj, self._lock:
             raw_data = array_from_file(self._shape,
                                        self._dtype,
                                        fileobj,

nibabel/openers.py

@@ -14,6 +14,13 @@
 import sys
 from os.path import splitext
 
+# is indexed_gzip present?
+try:
+    from indexed_gzip import SafeIndexedGzipFile
+    HAVE_INDEXED_GZIP = True
+except:
+    HAVE_INDEXED_GZIP = False
+
 
 # The largest memory chunk that gzip can use for reads
 GZIP_MAX_READ_CHUNK = 100 * 1024 * 1024  # 100Mb
@@ -62,13 +69,6 @@ def readinto(self, buf):
 
 def _gzip_open(fileish, mode='rb', compresslevel=9):
 
-    # is indexed_gzip present?
-    try:
-        from indexed_gzip import SafeIndexedGzipFile
-        have_indexed_gzip = True
-    except:
-        have_indexed_gzip = False
-
     # is this a file? if not we assume it is a string
     is_file = hasattr(fileish, 'read') and hasattr(fileish, 'write')
 
@@ -77,7 +77,7 @@ def _gzip_open(fileish, mode='rb', compresslevel=9):
         mode = fileish.mode
 
     # use indexed_gzip if possible for faster read access
-    if mode == 'rb' and have_indexed_gzip:
+    if mode == 'rb' and HAVE_INDEXED_GZIP:
         if is_file:
             gzip_file = SafeIndexedGzipFile(fid=fileish)
         else: