FIX: Update pyproj functions to take string. (#1589)

* FIX: Update pyproj functions to take string.

* STY: Update to use isinstance.

pyart/core/grid.py

@@ -170,26 +170,33 @@ def __setstate__(self, state):
     def projection_proj(self):
         # Proj instance as specified by the projection attribute.
         # Raises a ValueError if the pyart_aeqd projection is specified.
-        projparams = self.get_projparams()
-        if projparams["proj"] == "pyart_aeqd":
-            raise ValueError(
-                "Proj instance can not be made for the pyart_aeqd projection"
-            )
         if not _PYPROJ_AVAILABLE:
             raise MissingOptionalDependency(
                 "PyProj is required to create a Proj instance but it "
                 + "is not installed"
             )
+        projparams = self.get_projparams()
+
+        # Check if projparams is dictionary and check for pyart_aeqd
+        if isinstance(projparams, dict):
+            if projparams["proj"] == "pyart_aeqd":
+                raise ValueError(
+                    "Proj instance can not be made for the pyart_aeqd projection"
+                )
+        # Get proj instance from a proj str or dict
         proj = pyproj.Proj(projparams)
         return proj
 
     def get_projparams(self):
-        """Return a projparam dict from the projection attribute."""
-        projparams = self.projection.copy()
-        if projparams.pop("_include_lon_0_lat_0", False):
-            projparams["lon_0"] = self.origin_longitude["data"][0]
-            projparams["lat_0"] = self.origin_latitude["data"][0]
-        return projparams
+        """Return a projparam dict or str from the projection attribute."""
+        if isinstance(self.projection, dict):
+            projparams = self.projection.copy()
+            if projparams.pop("_include_lon_0_lat_0", False):
+                projparams["lon_0"] = self.origin_longitude["data"][0]
+                projparams["lat_0"] = self.origin_latitude["data"][0]
+            return projparams
+        else:
+            return self.projection
 
     def _find_and_check_nradar(self):
         """

tests/core/test_grid.py

@@ -307,6 +307,13 @@ def test_projection_proj():
     assert isinstance(grid.projection_proj, pyproj.Proj)
 
 
+@pytest.mark.skipif(not _PYPROJ_AVAILABLE, reason="PyProj is not installed.")
+def test_projection_proj_str():
+    grid = pyart.testing.make_target_grid()
+    grid.projection = "+proj=aeqd"
+    assert isinstance(grid.projection_proj, pyproj.Proj)
+
+
 def test_projection_proj_raised():
     grid = pyart.testing.make_target_grid()