ENH: File-like properties

Author: TomAugspurger

s3fs/core.py

@@ -503,6 +503,7 @@ def __init__(self, s3, path, mode='rb', block_size=5*2**20):
         self.start = None
         self.end = None
         self.closed = False
+        self._mode = mode
         if mode == 'wb':
             self.buffer = io.BytesIO()
             self.parts = []
@@ -520,6 +521,15 @@ def __init__(self, s3, path, mode='rb', block_size=5*2**20):
             except ClientError:
                 raise IOError("File not accessible", path)
 
+    def readable(self):
+        return self.mode == 'rb'
+
+    def seekable(self):
+        return self.readable()
+
+    def writable(self):
+        return self.mode == 'wb'
+
     def info(self):
         """ File information about this path """
         return self.s3.info(self.path)

s3fs/tests/test_s3fs.py

@@ -499,3 +499,26 @@ def test_write_blocks(s3):
         f.write(b'a' * 15*2**20)
         assert f.buffer.tell() == 0
     assert s3.info(test_bucket_name+'/temp')['Size'] == 15*2**20
+
+
+def test_readable(s3):
+    with s3.open(a, 'wb') as f:
+        assert not f.readable()
+
+    with s3.open(a, 'rb') as f:
+        assert f.readable()
+
+
+def test_seekable(s3):
+    with s3.open(a, 'wb') as f:
+        assert not f.seekable()
+
+    with s3.open(a, 'rb') as f:
+        assert f.seekable()
+
+def test_writable(s3):
+    with s3.open(a, 'wb') as f:
+        assert f.writable()
+
+    with s3.open(a, 'rb') as f:
+        assert not f.writable()