Add file arguments

f90nml/namelist.py

@@ -223,22 +223,30 @@ def false_repr(self, value):
     def write(self, nml_path, force=False):
         """Output dict to a Fortran 90 namelist file."""
 
-        if not force and os.path.isfile(nml_path):
+        nml_is_file = hasattr(nml_path, 'read')
+        if not force and not nml_is_file and os.path.isfile(nml_path):
             raise IOError('File {0} already exists.'.format(nml_path))
 
-        with open(nml_path, 'w') as nml_file:
-            for grp_name, grp_vars in self.items():
-                # Check for repeated namelist records (saved as lists)
-                if isinstance(grp_vars, list):
-                    for g_vars in grp_vars:
-                        self.write_nmlgrp(grp_name, g_vars, nml_file)
-                else:
-                    self.write_nmlgrp(grp_name, grp_vars, nml_file)
+        # collect individual (name, namelist) pairs, including repeated names
+        groups = []
+        for (name,vals) in self.items():
+            if isinstance(vals, list): # repeated namelist
+                groups.extend((name, v) for v in vals)
+            else:
+                groups.append((name, vals))
+
+        nml_file = nml_path if nml_is_file else open(nml_path, 'w')
+        try:
+            if len(groups) > 0:
+                first_name, first_vals = groups[0]
+                self.write_nmlgrp(first_name, first_vals, nml_file)
 
-        if self.items():
-            with open(nml_path, 'rb+') as nml_file:
-                nml_file.seek(-1, os.SEEK_END)
-                nml_file.truncate()
+                for (name, vals) in groups[1:]:
+                    print(file=nml_file) # double-space between groups
+                    self.write_nmlgrp(name, vals, nml_file)
+        finally:
+            if not nml_is_file:
+                nml_file.close()
 
     def write_nmlgrp(self, grp_name, grp_vars, nml_file):
         """Write namelist group to target file."""
@@ -255,7 +263,6 @@ def write_nmlgrp(self, grp_name, grp_vars, nml_file):
                 print(nml_line, file=nml_file)
 
         print('/', file=nml_file)
-        print(file=nml_file)
 
     def var_strings(self, v_name, v_values, v_idx=None):
         """Convert namelist variable to list of fixed-width strings."""

f90nml/parser.py

@@ -75,30 +75,39 @@ def read(self, nml_fname, nml_patch_in=None, patch_fname=None):
         >>> parser = Parser()
         >>> data_nml = parser.read('data.nml')"""
 
+        # For switching based on files versus paths
+        nml_is_path = not hasattr(nml_fname, 'read')
+        patch_is_path = not hasattr(patch_fname, 'read')
+
         # Convert patch data to a Namelist object
         if nml_patch_in:
             if not isinstance(nml_patch_in, dict):
                 raise ValueError('Input patch must be a dict or a Namelist.')
 
             nml_patch = copy.deepcopy(Namelist(nml_patch_in))
 
-            if not patch_fname:
+            if not patch_fname and nml_is_path:
                 patch_fname = nml_fname + '~'
+            elif not patch_fname:
+                raise ValueError('f90nml: error: No output file for patch.')
             elif nml_fname == patch_fname:
                 raise ValueError('f90nml: error: Patch filepath cannot be the '
                                  'same as the original filepath.')
-            self.pfile = open(patch_fname, 'w')
+            self.pfile = open(patch_fname, 'w') if patch_is_path else patch_fname
         else:
             nml_patch = Namelist()
 
         try:
-            nml_file = open(nml_fname, 'r')
-            return self.readstream(nml_file, nml_patch)
+            nml_file = open(nml_fname, 'r') if nml_is_path else nml_fname
+            try:
+                return self.readstream(nml_file, nml_patch)
 
+            # Close the files we opened on any exceptions within readstream
+            finally:
+                if nml_is_path:
+                    nml_file.close()
         finally:
-            # Close the unfinished files on any exceptions within readstream
-            nml_file.close()
-            if self.pfile:
+            if self.pfile and patch_is_path:
                 self.pfile.close()
 
     def readstream(self, nml_file, nml_patch):

test/test_f90nml.py

@@ -237,13 +237,27 @@ def assert_file_equal(self, source_fname, target_fname):
                 self.assertEqual(source_str, target_str)
 
     def assert_write(self, nml, target_fname):
+        self.assert_write_path(nml, target_fname)
+        self.assert_write_file(nml, target_fname)
+
+    def assert_write_path(self, nml, target_fname):
         tmp_fname = 'tmp.nml'
         f90nml.write(nml, tmp_fname)
         try:
             self.assert_file_equal(tmp_fname, target_fname)
         finally:
             os.remove(tmp_fname)
 
+    def assert_write_file(self, nml, target_fname):
+        tmp_fname = 'tmp.nml'
+        with open(tmp_fname, 'w') as tmp_file:
+            f90nml.write(nml, tmp_file)
+            self.assertFalse(tmp_file.closed)
+        try:
+            self.assert_file_equal(tmp_fname, target_fname)
+        finally:
+            os.remove(tmp_fname)
+
     # Tests
     def test_empty(self):
         test_nml = f90nml.read('empty.nml')
@@ -352,7 +366,7 @@ def test_pop_key(self):
         test_nml.pop('empty_nml')
         self.assertEqual(test_nml, f90nml.namelist.Namelist())
 
-    def test_patch(self):
+    def test_patch_paths(self):
         patch_nml = f90nml.read('types_patch.nml')
         f90nml.patch('types.nml', patch_nml, 'tmp.nml')
         test_nml = f90nml.read('tmp.nml')
@@ -361,6 +375,19 @@ def test_patch(self):
         finally:
             os.remove('tmp.nml')
 
+    def test_patch_files(self):
+        patch_nml = f90nml.read('types_patch.nml')
+        with open('types.nml') as f_in:
+            with open('tmp.nml', 'w') as f_out:
+                f90nml.patch(f_in, patch_nml, f_out)
+                self.assertFalse(f_in.closed)
+                self.assertFalse(f_out.closed)
+        try:
+            test_nml = f90nml.read('tmp.nml')
+            self.assertEqual(test_nml, patch_nml)
+        finally:
+            os.remove('tmp.nml')
+
     def test_patch_case(self):
         patch_nml = f90nml.read('types_patch.nml')
         f90nml.patch('types_uppercase.nml', patch_nml, 'tmp.nml')
@@ -383,6 +410,10 @@ def test_default_patch(self):
         finally:
             os.remove('types.nml~')
 
+        # The above behavior is only for paths, not files
+        with open('types.nml') as nml_file:
+            self.assertRaises(ValueError, f90nml.patch, nml_file, patch_nml)
+
     def test_no_selfpatch(self):
         patch_nml = f90nml.read('types_patch.nml')
         self.assertRaises(ValueError, f90nml.patch,