Allow writeProblem to write to stdout

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 ### Added
+- Added printProblem to print problem to stdout
 - Added stage checks to presolve, freereoptsolve, freetransform
 - Added primal_dual_evolution recipe and a plot recipe
 ### Fixed

src/pyscipopt/scip.pxi

@@ -272,7 +272,7 @@
     if rc == SCIP_OKAY:
         pass
     elif rc == SCIP_ERROR:
         raise Exception('SCIP: unspecified error!')
     elif rc == SCIP_NOMEMORY:
         raise MemoryError('SCIP: insufficient memory error!')
     elif rc == SCIP_READERROR:
@@ -2889,6 +2889,32 @@
         if not onlyroot:
             self.setIntParam("propagating/maxrounds", 0)
 
+    def printProblem(self, ext='.cip', trans=False, genericnames=False):
+        """
+        Write current model/problem to standard output.
+
+        Parameters
+        ----------
+        ext   : str, optional
+            the extension to be used (Default value = '.cip').
+            Should have an extension corresponding to one of the readable file formats,
+            described in https://www.scipopt.org/doc/html/group__FILEREADERS.php.
+        trans : bool, optional
+            indicates whether the transformed problem is written to file (Default value = False)
+        genericnames : bool, optional
+            indicates whether the problem should be written with generic variable
+            and constraint names (Default value = False)
+        """
+        user_locale = locale.getlocale(category=locale.LC_NUMERIC)
+        locale.setlocale(locale.LC_NUMERIC, "C")
+
+        if trans:
+            PY_SCIP_CALL(SCIPwriteTransProblem(self._scip, NULL, str_conversion(ext)[1:], genericnames))
+        else:
+            PY_SCIP_CALL(SCIPwriteOrigProblem(self._scip, NULL, str_conversion(ext)[1:], genericnames))            
+
+        locale.setlocale(locale.LC_NUMERIC,user_locale)
+
     def writeProblem(self, filename='model.cip', trans=False, genericnames=False, verbose=True):
         """
         Write current model/problem to a file.
@@ -2911,22 +2937,27 @@
         user_locale = locale.getlocale(category=locale.LC_NUMERIC)
         locale.setlocale(locale.LC_NUMERIC, "C")
 
-        str_absfile = abspath(filename)
-        absfile = str_conversion(str_absfile)
-        fn, ext = splitext(absfile)
-
-        if len(ext) == 0:
-            ext = str_conversion('.cip')
-        fn = fn + ext
-        ext = ext[1:]
-
-        if trans:
-            PY_SCIP_CALL(SCIPwriteTransProblem(self._scip, fn, ext, genericnames))
+        if filename:
+            str_absfile = abspath(filename)
+            absfile = str_conversion(str_absfile)
+            fn, ext = splitext(absfile)
+            if len(ext) == 0:
+                ext = str_conversion('.cip')
+            fn = fn + ext
+            ext = ext[1:]
+
+            if trans:
+                PY_SCIP_CALL(SCIPwriteTransProblem(self._scip, fn, ext, genericnames))
+            else:
+                PY_SCIP_CALL(SCIPwriteOrigProblem(self._scip, fn, ext, genericnames))
+
+            if verbose:
+                print('wrote problem to file ' + str_absfile)
         else:
-            PY_SCIP_CALL(SCIPwriteOrigProblem(self._scip, fn, ext, genericnames))
-
-        if verbose:
-            print('wrote problem to file ' + str_absfile)
+            if trans:
+                PY_SCIP_CALL(SCIPwriteTransProblem(self._scip, NULL, str_conversion('.cip')[1:], genericnames))
+            else:
+                PY_SCIP_CALL(SCIPwriteOrigProblem(self._scip, NULL, str_conversion('.cip')[1:], genericnames))            
 
         locale.setlocale(locale.LC_NUMERIC,user_locale)
 

tests/test_model.py

@@ -67,6 +67,7 @@ def test_model():
 
     s.writeProblem('model')
     s.writeProblem('model.lp')
+    s.printProblem()
 
     s.freeProb()
     s = Model()