vim.buffers is a map not a list.

python-buffers describes vim.buffers as a mapping object. python-buffer
documents that b.number where b is a Buffer object can be used as a
python-buffers key. I.e. b == vim.buffers[b.number] should be true if b
is a valid buffer object.

nvim.py was implementing vim.buffers as a RemoteSequence which doesn't
provide the aforementioned properties. This change implements it as a
Buffer object instead. The latter is a new class that implements the
hybrid sequence/map interface that python-buffers describes.

Author: asankah

README.md

@@ -169,7 +169,7 @@ bridge](http://vimdoc.sourceforge.net/htmldoc/if_pyth.html#python-vim)):
 # Create a python API session attached to unix domain socket created above:
 >>> nvim = attach('socket', path='/tmp/nvim')
 # Now do some work. 
->>> buffer = nvim.buffers[0] # Get the first buffer
+>>> buffer = nvim.current.buffer # Get the current buffer
 >>> buffer[0] = 'replace first line'
 >>> buffer[:] = ['replace whole buffer']
 >>> nvim.command('vsplit')

neovim/api/buffer.py

@@ -1,4 +1,4 @@
-"""API for working with Nvim buffers."""
+"""API for working with a Nvim Buffer."""
 from .common import Remote
 from ..compat import IS_PYTHON3
 

neovim/api/common.py

@@ -113,9 +113,9 @@ class RemoteSequence(object):
     sequences(of lines, buffers, windows and tabpages) with an API that
     is similar to the one provided by the python-vim interface.
 
-    For example, the 'buffers' property of the `Nvim class is a RemoteSequence
-    sequence instance, and the expression `nvim.buffers[0]` is translated to
-    session.request('vim_get_buffers')[0].
+    For example, the 'windows' property of the `Nvim` class is a RemoteSequence
+    sequence instance, and the expression `nvim.windows[0]` is translated to
+    session.request('vim_get_windows')[0].
 
     It can also receive an optional self_obj that will be passed as first
     argument of the request. For example, `tabpage.windows[0]` is translated

neovim/api/nvim.py

@@ -79,7 +79,7 @@ def __init__(self, session, channel_id, metadata, types,
         self.vars = RemoteMap(self, 'vim_get_var', 'vim_set_var')
         self.vvars = RemoteMap(self, 'vim_get_vvar', None)
         self.options = RemoteMap(self, 'vim_get_option', 'vim_set_option')
-        self.buffers = RemoteSequence(self, 'vim_get_buffers')
+        self.buffers = Buffers(self)
         self.windows = RemoteSequence(self, 'vim_get_windows')
         self.tabpages = RemoteSequence(self, 'vim_get_tabpages')
         self.current = Current(self)
@@ -331,6 +331,41 @@ def handler():
         self._session.threadsafe_call(handler)
 
 
+class Buffers(object):
+
+    """Remote NVim buffers.
+
+    Currently the interface for interacting with remote NVim buffers is the
+    `vim_get_buffers` msgpack-rpc function. Most methods fetch the list of
+    buffers from NVim.
+
+    Conforms to *python-buffers*.
+    """
+
+    def __init__(self, nvim):
+        """Initialize a Buffers object with Nvim object `nvim`."""
+        self._fetch_buffers = nvim.api.get_buffers
+
+    def __len__(self):
+        """Return the count of buffers."""
+        return len(self._fetch_buffers())
+
+    def __getitem__(self, number):
+        """Return the Buffer object matching buffer number `number`."""
+        for b in self._fetch_buffers():
+            if b.number == number:
+                return b
+        raise KeyError(number)
+
+    def __contains__(self, b):
+        """Return whether Buffer `b` is a known valid buffer."""
+        return isinstance(b, Buffer) and b.valid
+
+    def __iter__(self):
+        """Return an iterator over the list of buffers."""
+        return iter(self._fetch_buffers())
+
+
 class CompatibilitySession(object):
 
     """Helper class for API compatibility."""

test/test_vim.py

@@ -92,13 +92,29 @@ def test_options():
 
 @with_setup(setup=cleanup)
 def test_buffers():
+    buffers = []
+
+    # Number of elements
     eq(len(vim.buffers), 1)
-    eq(vim.buffers[0], vim.current.buffer)
+
+    # Indexing (by buffer number)
+    eq(vim.buffers[vim.current.buffer.number], vim.current.buffer)
+
+    buffers.append(vim.current.buffer)
     vim.command('new')
     eq(len(vim.buffers), 2)
-    eq(vim.buffers[1], vim.current.buffer)
-    vim.current.buffer = vim.buffers[0]
-    eq(vim.buffers[0], vim.current.buffer)
+    buffers.append(vim.current.buffer)
+    eq(vim.buffers[vim.current.buffer.number], vim.current.buffer)
+    vim.current.buffer = buffers[0]
+    eq(vim.buffers[vim.current.buffer.number], buffers[0])
+
+    # Membership test
+    ok(buffers[0] in vim.buffers)
+    ok(buffers[1] in vim.buffers)
+    ok({} not in vim.buffers)
+
+    # Iteration
+    eq(buffers, list(vim.buffers))
 
 
 @with_setup(setup=cleanup)