Merge pull request #97 from jimrybarski/96-context-manager

resolves #96: added context manager

README.md

@@ -52,6 +52,14 @@ You can also get some metadata about the nd2 programatically:
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 ```
 
+`Nd2` is also a context manager, if you care about that sort of thing:
+
+```
+>>> import nd2reader
+>>> with nd2reader.Nd2("/path/to/my_images.nd2") as nd2:
+...     for image in nd2:
+...         do_something(image)
+
 ### Images
 
 `Image` objects are just Numpy arrays with some extra metadata bolted on:

nd2reader/interface.py

@@ -12,12 +12,19 @@ class Nd2(object):
 
     """
     def __init__(self, filename):
+        self._filename = filename
         self._fh = open(filename, "rb")
         major_version, minor_version = get_version(self._fh)
         parser = get_parser(self._fh, major_version, minor_version)
         self._driver = parser.driver
         self._metadata = parser.metadata
-        self._filename = filename
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if self._fh is not None:
+            self._fh.close()
         
     def __repr__(self):
         return "\n".join(["<ND2 %s>" % self._filename,