Add type annotations for progress

lib/streamlit/elements/progress.py

@@ -12,15 +12,23 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import cast
+from typing import cast, TYPE_CHECKING, Union
+from typing_extensions import TypeAlias
 
-import streamlit
 from streamlit.errors import StreamlitAPIException
 from streamlit.proto.Progress_pb2 import Progress as ProgressProto
 
+if TYPE_CHECKING:
+    from streamlit.delta_generator import DeltaGenerator
+
+
+# Currently, equates to just float, but we can't use `numbers.Real` due to
+# https://github.com/python/mypy/issues/3186
+FloatOrInt: TypeAlias = Union[int, float]
+
 
 class ProgressMixin:
-    def progress(self, value):
+    def progress(self, value: FloatOrInt) -> "DeltaGenerator":
         """Display a progress bar.
 
         Parameters
@@ -46,29 +54,32 @@ def progress(self, value):
         # TODO: standardize numerical type checking across st.* functions.
         progress_proto = ProgressProto()
 
-        if isinstance(value, float):
-            if 0.0 <= value <= 1.0:
-                progress_proto.value = int(value * 100)
+        if isinstance(value, int):
+            if 0 <= value <= 100:
+                progress_proto.value = value
             else:
                 raise StreamlitAPIException(
-                    "Progress Value has invalid value [0.0, 1.0]: %f" % value
+                    "Progress Value has invalid value [0, 100]: %d" % value
                 )
 
-        elif isinstance(value, int):
-            if 0 <= value <= 100:
-                progress_proto.value = value
+        elif isinstance(value, float):
+            if 0.0 <= value <= 1.0:
+                progress_proto.value = int(value * 100)
             else:
                 raise StreamlitAPIException(
-                    "Progress Value has invalid value [0, 100]: %d" % value
+                    "Progress Value has invalid value [0.0, 1.0]: %f" % value
                 )
         else:
             raise StreamlitAPIException(
                 "Progress Value has invalid type: %s" % type(value).__name__
             )
 
-        return self.dg._enqueue("progress", progress_proto)
+        return cast(
+            "DeltaGenerator",
+            self.dg._enqueue("progress", progress_proto),
+        )
 
     @property
-    def dg(self) -> "streamlit.delta_generator.DeltaGenerator":
+    def dg(self) -> "DeltaGenerator":
         """Get our DeltaGenerator."""
-        return cast("streamlit.delta_generator.DeltaGenerator", self)
+        return cast("DeltaGenerator", self)