DOC: Add Python example equivalent to RNAfold -p --MEA

doc/refman.include/examples_python.dox

@@ -26,6 +26,12 @@ Boltzmann Sampling (a.k.a. Probabilistic Backtracing)
 -----------------------------------------------------
 @include  boltzmann_sampling.py
 
+@anchor examples_python_MEA
+
+RNAfold -p --MEA equivalent
+-----------------------------------------------------
+@include  RNAfold_MEA.py
+
 @anchor examples_python_soft_constraints
 
 Fun with Soft Constraints

examples/Makefile.am

@@ -28,7 +28,8 @@ examples_python = \
     Python/helloworld_nondefault.py \
     Python/maximum_matching.py \
     Python/oo_example1.py \
-    Python/subopt.py
+    Python/subopt.py \
+    Python/RNAfold_MEA.py
 
 data_files = \
     files/alignment_clustal.aln \

examples/Python/RNAfold_MEA.py

@@ -0,0 +1,37 @@
+#!/usr/bin/python
+#
+
+import RNA
+
+seq = "AUUUCCACUAGAGAAGGUCUAGAGUGUUUGUCGUUUGUCAGAAGUCCCUAUUCCAGGUACGAACACGGUGGAUAUGUUCGACGACAGGAUCGGCGCACUA"
+
+# create fold_compound data structure (required for all subsequently applied  algorithms)
+fc = RNA.fold_compound(seq)
+
+# compute MFE and MFE structure
+(mfe_struct, mfe) = fc.mfe()
+
+# rescale Boltzmann factors for partition function computation
+fc.exp_params_rescale(mfe)
+
+# compute partition function
+(pp, pf) = fc.pf()
+
+# compute centroid structure
+(centroid_struct, dist) = fc.centroid()
+
+# compute free energy of centroid structure
+centroid_en = fc.eval_structure(centroid_struct)
+
+# compute MEA structure
+(MEA_struct, MEA) = fc.MEA()
+
+# compute free energy of MEA structure
+MEA_en = fc.eval_structure(MEA_struct)
+
+# print everything like RNAfold -p --MEA
+print("%s\n%s (%6.2f)" % (seq, mfe_struct, mfe))
+print("%s [%6.2f]" % (pp, pf))
+print("%s {%6.2f d=%.2f}" % (centroid_struct, centroid_en, dist))
+print("%s {%6.2f MEA=%.2f}" % (MEA_struct, MEA_en, MEA))
+print(" frequency of mfe structure in ensemble %g; ensemble diversity %-6.2f" % (fc.pr_structure(mfe_struct), fc.mean_bp_distance()))