diff --git a/NEWS b/NEWS
index 595111478..f83b9d645 100644
--- a/NEWS
+++ b/NEWS
@@ -97,6 +97,12 @@ New in spot 2.0.3a (not yet released)
     not used anywhere in Spot, and had an obvious bug in its
     implementation, so it cannot be missed by anyone.
 
+  * spot::twa has two new methods that supplement is_empty():
+    twa::accepting_run() and twa::accepting_word().  They compute
+    what their name suggests.  Note that twa::accepting_run(), unlike
+    the two others, is currently restricted to automata with Fin-less
+    acceptance.
+
   Python:
 
   * The __format__() method for formula support the same
diff --git a/bin/autfilt.cc b/bin/autfilt.cc
index 83ae1d9d3..5c4d8eca3 100644
--- a/bin/autfilt.cc
+++ b/bin/autfilt.cc
@@ -1019,9 +1019,8 @@ namespace
             if (aut->acc().uses_fin_acceptance())
               error(2, 0,
                     "--highlight-word does not yet work with Fin acceptance");
-            if (auto res =
-                spot::couvreur99(spot::product(aut, word_aut.first))->check())
-              res->accepting_run()->project(aut)->highlight(word_aut.second);
+            if (auto run = spot::product(aut, word_aut.first)->accepting_run())
+              run->project(aut)->highlight(word_aut.second);
           }
 
       const double conversion_time = sw.stop();
diff --git a/bin/common_aoutput.hh b/bin/common_aoutput.hh
index af0a6a581..9df32fda9 100644
--- a/bin/common_aoutput.hh
+++ b/bin/common_aoutput.hh
@@ -178,15 +178,10 @@ public:
         }
     if (has('w'))
         {
-          auto res = spot::couvreur99(aut)->check();
-          if (res)
+          if (auto word = aut->accepting_word())
             {
-              auto run = res->accepting_run();
-              assert(run);
-              spot::twa_word w(run->reduce());
-              w.simplify();
               std::ostringstream out;
-              out << w;
+              out << *word;
               aut_word_ = out.str();
             }
           else
diff --git a/bin/ltlcross.cc b/bin/ltlcross.cc
index eab9f299a..dd5439b16 100644
--- a/bin/ltlcross.cc
+++ b/bin/ltlcross.cc
@@ -682,8 +682,8 @@ namespace
         std::cerr << '\n';
       }
 
-    auto res = spot::couvreur99(prod)->check();
-    if (res)
+    auto w = prod->accepting_word();
+    if (w)
       {
         std::ostream& err = global_error();
         err << "error: ";
@@ -695,24 +695,12 @@ namespace
           err << "*Comp(P" << j << ')';
         else
           err << "*N" << j;
-        err << " is nonempty";
-
-        auto run = res->accepting_run();
-        if (run)
-          {
-            std::cerr << "; both automata accept the infinite word\n"
-                      << "       ";
-            spot::twa_word w(run->reduce());
-            w.simplify();
-            example() << w << '\n';
-          }
-        else
-          {
-            std::cerr << '\n';
-          }
+        err << " is nonempty; both automata accept the infinite word\n"
+            << "       ";
+        example() << *w << '\n';
         end_error();
       }
-    return !!res;
+    return !!w;
   }
 
   static bool
diff --git a/spot/twa/twa.cc b/spot/twa/twa.cc
index 2b8b0d169..92d29adb2 100644
--- a/spot/twa/twa.cc
+++ b/spot/twa/twa.cc
@@ -23,6 +23,7 @@
 #include <spot/twa/twa.hh>
 #include <spot/twa/twagraph.hh>
 #include <spot/twaalgos/gtec/gtec.hh>
+#include <spot/twaalgos/word.hh>
 #include <spot/twaalgos/remfin.hh>
 #include <utility>
 
@@ -69,6 +70,42 @@ namespace spot
     return !couvreur99(a)->check();
   }
 
+  twa_run_ptr
+  twa::accepting_run() const
+  {
+    if (acc().uses_fin_acceptance())
+      throw std::runtime_error("twa::accepting_run() does not work with "
+                               "Fin acceptance (but twa:is_empty() and "
+                               "twa::accepting_run() can)");
+    auto res = couvreur99(shared_from_this())->check();
+    if (!res)
+      return nullptr;
+    return res->accepting_run();
+  }
+
+  twa_word_ptr
+  twa::accepting_word() const
+  {
+    auto a = shared_from_this();
+    if (a->acc().uses_fin_acceptance())
+      {
+        auto aa = std::dynamic_pointer_cast<const twa_graph>(a);
+        if (!aa)
+          aa = make_twa_graph(a, prop_set::all());
+        a = remove_fin(aa);
+      }
+    if (auto run = a->accepting_run())
+      {
+        auto w = make_twa_word(run->reduce());
+        w->simplify();
+        return w;
+      }
+    else
+      {
+        return nullptr;
+      }
+  }
+
   void
   twa::set_named_prop(std::string s, std::nullptr_t)
   {
diff --git a/spot/twa/twa.hh b/spot/twa/twa.hh
index 2a7d707e9..d5f06dbb9 100644
--- a/spot/twa/twa.hh
+++ b/spot/twa/twa.hh
@@ -39,6 +39,12 @@
 
 namespace spot
 {
+  struct twa_run;
+  typedef std::shared_ptr<twa_run> twa_run_ptr;
+
+  struct twa_word;
+  typedef std::shared_ptr<twa_word> twa_word_ptr;
+
   /// \ingroup twa_essentials
   /// \brief Abstract class for states.
   class SPOT_API state
@@ -821,9 +827,28 @@ namespace spot
     }
     ///@}
 
-    /// Check whether the language of the automaton is empty.
+    /// \brief Check whether the language of the automaton is empty.
     virtual bool is_empty() const;
 
+    /// \brief Return an accepting run if one exists.
+    ///
+    /// Note that this method currently one works for Fin-less
+    /// acceptance.  For acceptance conditions that contain Fin
+    /// acceptance, you can either rely on is_empty() and not use any
+    /// accepting run, or remove Fin acceptance using remove_fin() and
+    /// compute an accepting run on that larger automaton.
+    ///
+    /// Return nullptr if no accepting run were found.
+    virtual twa_run_ptr accepting_run() const;
+
+    /// \brief Return an accepting word if one exists.
+    ///
+    /// Note that this method DO works with Fin
+    /// acceptance.
+    ///
+    /// Return nullptr if no accepting word were found.
+    virtual twa_word_ptr accepting_word() const;
+
   private:
     acc_cond acc_;
 
diff --git a/tests/python/highlighting.ipynb b/tests/python/highlighting.ipynb
index 5804bd265..49703bf95 100644
--- a/tests/python/highlighting.ipynb
+++ b/tests/python/highlighting.ipynb
@@ -18,7 +18,7 @@
    "version": "3.4.3+"
   },
   "name": "",
-  "signature": "sha256:0f4fb50930c6511a58891626864fe3236e91bb2525f9d8b2b1108f3e2a4c5d28"
+  "signature": "sha256:f8755e90b26b56799cf6192d76999196f60eefa8307d0d104b73f476904754cc"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -155,7 +155,7 @@
         "</svg>"
        ],
        "text": [
-        "<IPython.core.display.SVG at 0x7f44a034f208>"
+        "<IPython.core.display.SVG at 0x7f859c2ba588>"
        ]
       }
      ],
@@ -255,7 +255,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a00f88a0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f859c0838a0> >"
        ]
       }
      ],
@@ -357,7 +357,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.twa; proxy of <Swig Object of type 'std::shared_ptr< spot::twa > *' at 0x7f44a006cf30> >"
+        "<spot.twa; proxy of <Swig Object of type 'std::shared_ptr< spot::twa > *' at 0x7f8595d88f60> >"
        ]
       }
      ],
@@ -572,7 +572,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a006cfc0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f8595d88fc0> >"
        ]
       }
      ],
@@ -582,7 +582,7 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "r = spot.couvreur99(b).check().accepting_run(); r"
+      "r = b.accepting_run(); r"
      ],
      "language": "python",
      "metadata": {},
@@ -751,7 +751,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a006cfc0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f8595d88fc0> >"
        ]
       }
      ],
@@ -831,7 +831,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a68f50f0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f85a187e090> >"
        ]
       },
       {
@@ -877,7 +877,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a68f50c0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f85a187e060> >"
        ]
       }
      ],
@@ -963,7 +963,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a006cf60> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f8595d88d20> >"
        ]
       }
      ],
@@ -973,7 +973,7 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "run = spot.couvreur99(prod).check().accepting_run(); run"
+      "run = prod.accepting_run(); run"
      ],
      "language": "python",
      "metadata": {},
@@ -1088,7 +1088,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a006cf60> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f8595d88d20> >"
        ]
       },
       {
@@ -1145,7 +1145,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a68f50f0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f85a187e090> >"
        ]
       },
       {
@@ -1191,7 +1191,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a68f50c0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f85a187e060> >"
        ]
       }
      ],
@@ -1211,7 +1211,7 @@
       "left2 = spot.translate('!b & FG a')\n",
       "right2 = spot.translate('XXXb')\n",
       "prod2 = spot.otf_product(left2, right2)  # Note \"otf_product()\"\n",
-      "run2 = spot.couvreur99(prod2).check().accepting_run()\n",
+      "run2 = prod2.accepting_run()\n",
       "run2.project(left2).highlight(5)\n",
       "run2.project(right2, True).highlight(5)\n",
       "display(run2, prod2, left2, right2)"
@@ -1398,7 +1398,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_product; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_product > *' at 0x7f44a68f5120> >"
+        "<spot.impl.twa_product; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_product > *' at 0x7f85a187e120> >"
        ]
       },
       {
@@ -1472,7 +1472,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a68f5060> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f85a187e0f0> >"
        ]
       },
       {
@@ -1556,7 +1556,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a68f5030> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f85a187e150> >"
        ]
       }
      ],
@@ -1702,7 +1702,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f44a68f5210> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f85a187e240> >"
        ]
       }
      ],
diff --git a/tests/python/word.ipynb b/tests/python/word.ipynb
index ad820de94..7e554b7d3 100644
--- a/tests/python/word.ipynb
+++ b/tests/python/word.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:261c16336ba5deefb7e9ebe705cc5c24f1cbba8622030874d2719f5045289c53"
+  "signature": "sha256:4fc3934cf5fa0e612923dc4253b5e40115b103a93f588595a6706ec77e7994a9"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -139,7 +139,7 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7fa33c302870> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7fb71c0e18a0> >"
        ]
       }
      ],
@@ -149,17 +149,14 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "The call to `couvreur99()` just instanciate the emptiness check, but does not run the check.  Calling `check()` will return `None` if no accepting run was found.  Otherwise the presence of the accepting run is established, but an accepting run hasn't necessarily been calculated: calling `accepting_run()` on the result will cause this computation to happen.\n",
-      "\n",
-      "\n",
-      "In the example below, we do not check the result of `check()` because we know that the input formula is satisfiable, so the automaton has an accepting run."
+      "Build an accepting run:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "run = spot.couvreur99(aut).check().accepting_run(); run"
+      "run = aut.accepting_run(); run"
      ],
      "language": "python",
      "metadata": {},
@@ -295,6 +292,33 @@
      ],
      "prompt_number": 7
     },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Such a simplified word can be created directly from the automaton:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "aut.accepting_word()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 8,
+       "text": [
+        "cycle{!a & b; a & b}"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
     {
      "cell_type": "markdown",
      "metadata": {},
@@ -323,7 +347,7 @@
        ]
       }
      ],
-     "prompt_number": 8
+     "prompt_number": 9
     },
     {
      "cell_type": "code",
@@ -338,13 +362,13 @@
       {
        "metadata": {},
        "output_type": "pyout",
-       "prompt_number": 9,
+       "prompt_number": 10,
        "text": [
         "a; a & b; cycle{!a & !b}"
        ]
       }
      ],
-     "prompt_number": 9
+     "prompt_number": 10
     },
     {
      "cell_type": "markdown",
@@ -362,7 +386,7 @@
      "language": "python",
      "metadata": {},
      "outputs": [],
-     "prompt_number": 10
+     "prompt_number": 11
     },
     {
      "cell_type": "code",
@@ -376,7 +400,7 @@
       {
        "metadata": {},
        "output_type": "pyout",
-       "prompt_number": 11,
+       "prompt_number": 12,
        "svg": [
         "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n",
         "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\"\n",
@@ -454,17 +478,17 @@
         "</svg>\n"
        ],
        "text": [
-        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7fa33c3028d0> >"
+        "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7fb71c0e1a20> >"
        ]
       }
      ],
-     "prompt_number": 11
+     "prompt_number": 12
     },
     {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Test some syntax errors"
+      "The rest of this pages tests some syntax errors, you (humans) may skip it, but the test suite will not."
      ]
     },
     {
@@ -485,7 +509,7 @@
        ]
       }
      ],
-     "prompt_number": 12
+     "prompt_number": 13
     },
     {
      "cell_type": "code",
@@ -505,7 +529,7 @@
        ]
       }
      ],
-     "prompt_number": 13
+     "prompt_number": 14
     },
     {
      "cell_type": "code",
@@ -525,7 +549,7 @@
        ]
       }
      ],
-     "prompt_number": 14
+     "prompt_number": 15
     },
     {
      "cell_type": "code",
@@ -545,7 +569,7 @@
        ]
       }
      ],
-     "prompt_number": 15
+     "prompt_number": 16
     },
     {
      "cell_type": "code",
@@ -557,7 +581,7 @@
      "language": "python",
      "metadata": {},
      "outputs": [],
-     "prompt_number": 16
+     "prompt_number": 17
     },
     {
      "cell_type": "code",
@@ -575,13 +599,13 @@
        "output_type": "pyerr",
        "traceback": [
         "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mRuntimeError\u001b[0m                              Traceback (most recent call last)",
-        "\u001b[0;32m<ipython-input-17-971829bb8f5f>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# ... as long as this word is not printed.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mw\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
-        "\u001b[0;32m/home/adl/git/spot/python/spot/impl.py\u001b[0m in \u001b[0;36m__str__\u001b[0;34m(self)\u001b[0m\n\u001b[1;32m   3511\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   3512\u001b[0m     \u001b[0;32mdef\u001b[0m \u001b[0m__str__\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m->\u001b[0m \u001b[0;34m\"std::string\"\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m-> 3513\u001b[0;31m         \u001b[0;32mreturn\u001b[0m \u001b[0m_impl\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtwa_word___str__\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m   3514\u001b[0m \u001b[0mtwa_word_swigregister\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0m_impl\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtwa_word_swigregister\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   3515\u001b[0m \u001b[0mtwa_word_swigregister\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mtwa_word\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+        "\u001b[0;32m<ipython-input-18-971829bb8f5f>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# ... as long as this word is not printed.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mw\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+        "\u001b[0;32m/home/adl/git/spot/python/spot/impl.py\u001b[0m in \u001b[0;36m__str__\u001b[0;34m(self)\u001b[0m\n\u001b[1;32m   3599\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   3600\u001b[0m     \u001b[0;32mdef\u001b[0m \u001b[0m__str__\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;34m->\u001b[0m \u001b[0;34m\"std::string\"\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m-> 3601\u001b[0;31m         \u001b[0;32mreturn\u001b[0m \u001b[0m_impl\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtwa_word___str__\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m   3602\u001b[0m \u001b[0mtwa_word_swigregister\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0m_impl\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtwa_word_swigregister\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m   3603\u001b[0m \u001b[0mtwa_word_swigregister\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mtwa_word\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
         "\u001b[0;31mRuntimeError\u001b[0m: a twa_word may not have an empty cycle"
        ]
       }
      ],
-     "prompt_number": 17
+     "prompt_number": 18
     }
    ],
    "metadata": {}