patch.diff

diff --git a/f90nml/parser.py b/f90nml/parser.py
index 687de10..7fb42d7 100644
--- a/f90nml/parser.py
+++ b/f90nml/parser.py
@@ -75,25 +75,39 @@ class Parser(object):
         >>> parser = Parser()
         >>> data_nml = parser.read('data.nml')"""
 
-        nml_file = open(nml_fname, 'r')
+        nml_is_file = hasattr(nml_fname, 'read')
+        nml_file = nml_fname if nml_is_file else open(nml_fname, 'r')
 
+        try:
             if nml_patch_in:
                 if not isinstance(nml_patch_in, dict):
-                nml_file.close()
-                raise ValueError('Input patch must be a dict or a Namelist.')
+                    raise ValueError('Input patch must be a dict or a '
+                                     'Namelist.')
 
                 nml_patch = copy.deepcopy(Namelist(nml_patch_in))
 
                 if not patch_fname:
                     patch_fname = nml_fname + '~'
                 elif nml_fname == patch_fname:
-                nml_file.close()
-                raise ValueError('f90nml: error: Patch filepath cannot be the '
-                                 'same as the original filepath.')
-            self.pfile = open(patch_fname, 'w')
+                    raise ValueError('f90nml: error: Patch filepath cannot be '
+                                     'the same as the original filepath.')
+
+                patch_is_file = hasattr(patch_fname, 'read')
+                self.pfile = patch_fname if patch_is_file else open(patch_fname, 'w')
             else:
                 nml_patch = Namelist()
 
+            return self._read(nml_file, nml_patch)
+
+        finally:
+            if not nml_is_file:
+                nml_file.close()
+            if self.pfile and not patch_is_file:
+                self.pfile.close()
+
+    def _read(self, nml_file, nml_patch):
+        """ implementaton of read given an open file handle and a Namelist """
+
         f90lex = shlex.shlex(nml_file)
         f90lex.whitespace = ''
         f90lex.wordchars += '.-+'       # Include floating point tokens
@@ -140,14 +154,8 @@ class Parser(object):
                 # Set the next active variable
                 if self.token in ('=', '(', '%'):
 
-                    try:
-                        v_name, v_values = self.parse_variable(
-                            g_vars, patch_nml=grp_patch)
-                    except ValueError:
-                        nml_file.close()
-                        if self.pfile:
-                            self.pfile.close()
-                        raise
+                    v_name, v_values = self.parse_variable(g_vars,
+                                                           patch_nml=grp_patch)
 
                     if v_name in g_vars:
                         v_prior_values = g_vars[v_name]
@@ -195,10 +203,6 @@ class Parser(object):
             except StopIteration:
                 break
 
-        nml_file.close()
-        if self.pfile:
-            self.pfile.close()
-
         return nmls
 
     def parse_variable(self, parent, patch_nml=None):

slightly-less-crap.diff

diff --git a/f90nml/parser.py b/f90nml/parser.py
index 6a582f5..44a72cf 100644
--- a/f90nml/parser.py
+++ b/f90nml/parser.py
@@ -75,6 +75,9 @@ class Parser(object):
         >>> parser = Parser()
         >>> data_nml = parser.read('data.nml')"""
 
+        nml_is_file = hasattr(nml_fname, 'read')
+        patch_is_file = hasattr(patch_fname, 'read')
+
         # Convert patch data to a Namelist object
         if nml_patch_in:
             if not isinstance(nml_patch_in, dict):
@@ -83,15 +86,37 @@ class Parser(object):
             nml_patch = copy.deepcopy(Namelist(nml_patch_in))
 
             if not patch_fname:
-                patch_fname = nml_fname + '~'
+                if nml_is_file:
+                    # TODO - probably ValueError: No output file for patch, or
+                    #  maybe warning?
+                else:
+                    patch_fname = nml_fname + '~'
             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 = patch_fname if patch_is_file else open(patch_fname, 'w')
         else:
             nml_patch = Namelist()
 
-        nml_file = open(nml_fname, 'r')
+        # auto-close self.pfile
+        try:
+            nml_file = nml_fname if nml_is_file else open(nml_fname, 'r')
+
+            # auto-close nml_file
+            try:
+
+                return self._read(nml_file, nml_patch)
+
+            finally:
+                if not nml_is_file:
+                    nml_file.close()
+        finally:
+            if self.pfile and not patch_is_file:
+                self.pfile.close()
+
+    def _read(self, nml_file, nml_patch):
+        """ implementaton of read given an open file handle and a Namelist """
 
         f90lex = shlex.shlex(nml_file)
         f90lex.whitespace = ''
@@ -139,14 +164,8 @@ class Parser(object):
                 # Set the next active variable
                 if self.token in ('=', '(', '%'):
 
-                    try:
-                        v_name, v_values = self.parse_variable(
-                            g_vars, patch_nml=grp_patch)
-                    except ValueError:
-                        nml_file.close()
-                        if self.pfile:
-                            self.pfile.close()
-                        raise
+                    v_name, v_values = self.parse_variable(
+                        g_vars, patch_nml=grp_patch)
 
                     if v_name in g_vars:
                         v_prior_values = g_vars[v_name]
@@ -194,10 +213,6 @@ class Parser(object):
             except StopIteration:
                 break
 
-        nml_file.close()
-        if self.pfile:
-            self.pfile.close()
-
         return nmls
 
     def parse_variable(self, parent, patch_nml=None):