[python] Fix string problems + Documentation.

- use bytes instead of char*
- add some basic docstrings to functions/constructors

1 files changed, 10 insertions, 9 deletions

diff --git a/python/src/lattice.pxi b/python/src/lattice.pxi
index 57e340d2..8000b61e 100644
--- a/python/src/lattice.pxi
+++ b/python/src/lattice.pxi
@@ -7,16 +7,16 @@ cdef class Lattice:
         self.lattice = new lattice.Lattice()
 
     def __init__(self, inp):
+        """Lattice(tuple) -> Lattice from node list.
+        Lattice(string) -> Lattice from PLF representation."""
         if isinstance(inp, tuple):
             self.lattice.resize(len(inp))
             for i, arcs in enumerate(inp):
                 self[i] = arcs
+        elif isinstance(inp, basestring):
+            lattice.ConvertTextOrPLF(as_str(inp), self.lattice)
         else:
-            if isinstance(inp, unicode):
-                inp = inp.encode('utf8')
-            if not isinstance(inp, str):
-                raise TypeError('cannot create lattice from %s' % type(inp))
-            lattice.ConvertTextOrPLF(string(<char *>inp), self.lattice)
+            raise TypeError('cannot create lattice from %s' % type(inp))
 
     def __dealloc__(self):
         del self.lattice
@@ -39,9 +39,8 @@ cdef class Lattice:
             raise IndexError('lattice index out of range')
         cdef lattice.LatticeArc* arc
         for (label, cost, dist2next) in arcs:
-            if isinstance(label, unicode):
-                label = label.encode('utf8')
-            arc = new lattice.LatticeArc(TDConvert(<char *>label), cost, dist2next)
+            label_str = as_str(label)
+            arc = new lattice.LatticeArc(TDConvert(label_str), cost, dist2next)
             self.lattice[0][index].push_back(arc[0])
             del arc
 
@@ -60,6 +59,7 @@ cdef class Lattice:
             yield self[i]
 
     def todot(self):
+        """lattice.todot() -> Representation of the lattice in GraphViz dot format."""
         def lines():
             yield 'digraph lattice {'
             yield 'rankdir = LR;'
@@ -72,8 +72,9 @@ cdef class Lattice:
         return '\n'.join(lines()).encode('utf8')
 
     def as_hypergraph(self):
+        """lattice.as_hypergraph() -> Hypergraph representation of the lattice."""
         cdef Hypergraph result = Hypergraph.__new__(Hypergraph)
         result.hg = new hypergraph.Hypergraph()
         cdef bytes plf = str(self)
-        hypergraph.ReadFromPLF(string(plf), result.hg)
+        hypergraph.ReadFromPLF(plf, result.hg)
         return result