[msm-model] minor improvements (markovmodel#828)

* explicit exception handling (AttributeError)
* pcca: convert argument to int

pyemma/msm/models/msm.py

@@ -88,8 +88,6 @@ def __init__(self, P, pi=None, reversible=None, dt_model='1 step', neig=None, nc
         self.set_model_params(P=P, pi=pi, reversible=reversible, dt_model=dt_model, neig=neig)
         self.ncv = ncv
 
-
-
     # TODO: maybe rename to parametrize in order to avoid confusion with set_params that has a different behavior?
     def set_model_params(self, P=None, pi=None, reversible=None, dt_model='1 step', neig=None):
         """ Call to set all basic model parameters.
@@ -206,8 +204,9 @@ def transition_matrix(self):
         """
         try:
             return self.P
-        except:
-            raise AttributeError('MSM has not yet been parametrized. Call __init__ or set transition matrix')
+        except AttributeError:
+            raise AttributeError('MSM has not yet been parametrized.'
+                                 'Call "MSM(P)", set_model_params(P=P) or set transition matrix')
 
     ################################################################################
     # Spectral quantities
@@ -243,7 +242,7 @@ def _ensure_eigenvalues(self, neig=None):
             if m < neig:
                 # not enough eigenpairs present - recompute:
                 self._compute_eigenvalues(neig)
-        except:
+        except AttributeError:
             # no eigendecomposition yet - compute:
             self._compute_eigenvalues(neig)
 
@@ -278,7 +277,7 @@ def _ensure_eigendecomposition(self, neig=None):
             if m < neig:
                 # not enough eigenpairs present - recompute:
                 self._compute_eigendecomposition(neig)
-        except:
+        except AttributeError:
             # no eigendecomposition yet - compute:
             self._compute_eigendecomposition(neig)
 
@@ -810,7 +809,7 @@ def _assert_metastable(self):
         try:
             if not self._metastable_computed:
                 raise ValueError('Metastable decomposition has not yet been computed. Please call pcca(m) first.')
-        except:
+        except AttributeError:
             raise ValueError('Metastable decomposition has not yet been computed. Please call pcca(m) first.')
 
     def pcca(self, m):
@@ -847,6 +846,7 @@ def pcca(self, m):
             (2): 147-179
 
         """
+        m = int(m)
         # can we do it?
         if not self.reversible:
             raise ValueError(
@@ -859,7 +859,7 @@ def pcca(self, m):
             if self._pcca.n_metastable != m:
                 # incorrect number of states - recompute
                 self._pcca = PCCA(self.transition_matrix, m)
-        except:
+        except AttributeError:
             # didn't have a pcca object yet - compute
             self._pcca = PCCA(self.transition_matrix, m)