Fix Velocity import (#579)

Fix Velocity import

Author: davidbrochart

docs/source/api_reference/velocity.rst

@@ -6,7 +6,8 @@ Example
 
 .. jupyter-execute::
 
-    from ipyleaflet import Map, Velocity, TileLayer, basemaps
+    from ipyleaflet import Map, TileLayer, basemaps
+    from ipyleaflet.velocity import Velocity
     import xarray as xr
     import os
 

ipyleaflet/leaflet.py

@@ -21,10 +21,6 @@
 
 from branca.colormap import linear, ColorMap
 
-from traittypes import Dataset
-
-from .xarray_ds import ds_x_to_json
-
 from ._version import EXTENSION_VERSION
 
 def_loc = [0.0, 0.0]
@@ -329,59 +325,6 @@ class VideoOverlay(RasterLayer):
     attribution = Unicode().tag(sync=True, o=True)
 
 
-class Velocity(Layer):
-    try:
-        import xarray
-    except ModuleNotFoundError:
-        raise ImportError(
-            'The `xarray` module (required for use of the Velocity layer) is '
-            'not installed.'
-        )
-
-    _view_name = Unicode('LeafletVelocityView').tag(sync=True)
-    _model_name = Unicode('LeafletVelocityModel').tag(sync=True)
-
-    zonal_speed = Unicode('', help='Name of the zonal speed in the dataset')
-    meridional_speed = Unicode('', help='Name of the meridional speed in the dataset')
-    latitude_dimension = Unicode('latitude', help='Name of the latitude dimension in the dataset')
-    longitude_dimension = Unicode('longitude', help='Name of the longitude dimension in the dataset')
-    units = Unicode(None, allow_none=True)
-
-    data = Dataset().tag(dtype=None, sync=True, to_json=ds_x_to_json)
-
-    # Options
-    display_values = Bool(True).tag(sync=True, o=True)
-    display_options = Dict({
-        'velocityType': 'Global Wind',
-        'position': 'bottomleft',
-        'emptyString': 'No velocity data',
-        'angleConvention': 'bearingCW',
-        'displayPosition': 'bottomleft',
-        'displayEmptyString': 'No velocity data',
-        'speedUnit': 'kt'
-    }).tag(sync=True)
-    min_velocity = Float(0).tag(sync=True, o=True)
-    max_velocity = Float(10).tag(sync=True, o=True)
-    velocity_scale = Float(0.005).tag(sync=True, o=True)
-    color_scale = List([
-        "rgb(36,104, 180)",
-        "rgb(60,157, 194)",
-        "rgb(128,205,193)",
-        "rgb(151,218,168)",
-        "rgb(198,231,181)",
-        "rgb(238,247,217)",
-        "rgb(255,238,159)",
-        "rgb(252,217,125)",
-        "rgb(255,182,100)",
-        "rgb(252,150,75)",
-        "rgb(250,112,52)",
-        "rgb(245,64,32)",
-        "rgb(237,45,28)",
-        "rgb(220,24,32)",
-        "rgb(180,0,35)"
-    ]).tag(sync=True, o=True)
-
-
 class Heatmap(RasterLayer):
     _view_name = Unicode('LeafletHeatmapView').tag(sync=True)
     _model_name = Unicode('LeafletHeatmapModel').tag(sync=True)

ipyleaflet/velocity.py

@@ -0,0 +1,54 @@
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+#
+
+from traittypes import Dataset
+from traitlets import Unicode, Bool, Dict, Float, List
+
+from .leaflet import Layer
+from .xarray_ds import ds_x_to_json
+
+
+class Velocity(Layer):
+    _view_name = Unicode('LeafletVelocityView').tag(sync=True)
+    _model_name = Unicode('LeafletVelocityModel').tag(sync=True)
+
+    zonal_speed = Unicode('', help='Name of the zonal speed in the dataset')
+    meridional_speed = Unicode('', help='Name of the meridional speed in the dataset')
+    latitude_dimension = Unicode('latitude', help='Name of the latitude dimension in the dataset')
+    longitude_dimension = Unicode('longitude', help='Name of the longitude dimension in the dataset')
+    units = Unicode(None, allow_none=True)
+
+    data = Dataset().tag(dtype=None, sync=True, to_json=ds_x_to_json)
+
+    # Options
+    display_values = Bool(True).tag(sync=True, o=True)
+    display_options = Dict({
+        'velocityType': 'Global Wind',
+        'position': 'bottomleft',
+        'emptyString': 'No velocity data',
+        'angleConvention': 'bearingCW',
+        'displayPosition': 'bottomleft',
+        'displayEmptyString': 'No velocity data',
+        'speedUnit': 'kt'
+    }).tag(sync=True)
+    min_velocity = Float(0).tag(sync=True, o=True)
+    max_velocity = Float(10).tag(sync=True, o=True)
+    velocity_scale = Float(0.005).tag(sync=True, o=True)
+    color_scale = List([
+        "rgb(36,104, 180)",
+        "rgb(60,157, 194)",
+        "rgb(128,205,193)",
+        "rgb(151,218,168)",
+        "rgb(198,231,181)",
+        "rgb(238,247,217)",
+        "rgb(255,238,159)",
+        "rgb(252,217,125)",
+        "rgb(255,182,100)",
+        "rgb(252,150,75)",
+        "rgb(250,112,52)",
+        "rgb(245,64,32)",
+        "rgb(237,45,28)",
+        "rgb(220,24,32)",
+        "rgb(180,0,35)"
+    ]).tag(sync=True, o=True)