ENH: lib: break reference cycle in NpzFile (#2048)

This allows these objects to be freed by refcount, rather than requiring
the gc, which can be useful in some situations.

1 files changed, 4 insertions, 1 deletions

diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py
index 3a575a048..c502e2cc5 100644
--- a/numpy/lib/npyio.py
+++ b/numpy/lib/npyio.py
@@ -10,6 +10,7 @@ import re
 import sys
 import itertools
 import warnings
+import weakref
 from operator import itemgetter
 
 from cPickle import load as _cload, loads
@@ -108,7 +109,8 @@ class BagObj(object):
 
     """
     def __init__(self, obj):
-        self._obj = obj
+        # Use weakref to make NpzFile objects collectable by refcount
+        self._obj = weakref.proxy(obj)
     def __getattribute__(self, key):
         try:
             return object.__getattribute__(self, '_obj')[key]
@@ -212,6 +214,7 @@ class NpzFile(object):
         if self.fid is not None:
             self.fid.close()
             self.fid = None
+        self.f = None # break reference cycle
 
     def __del__(self):
         self.close()