Added init tests to check lazy imports

Author: jonmmease

packages/python/plotly/plotly/__init__.py

@@ -55,6 +55,10 @@
         "colors",
         "__version__",
     ]
+
+    # Set default template (for >= 3.7 this is done in ploty/io/__init__.py)
+    from plotly.io import templates
+    templates._default = "plotly"
 else:
     __all__, __getattr__ = relative_import(
         __name__,
@@ -68,6 +72,7 @@
             ".io",
             ".data",
             ".colors",
+            ".express",
         ],
         [".version.__version__"],
     )
@@ -76,7 +81,4 @@
     # TODO: come back to _docstring_gen
     # from plotly import _docstring_gen
 
-# TODO: Set default template here to make sure import process is complete
-from plotly.io import templates
 
-templates._default = "plotly"

packages/python/plotly/plotly/io/__init__.py

@@ -45,3 +45,7 @@
             "._renderers.show",
         ],
     )
+
+    # Set default template (for < 3.7 this is done in ploty/__init__.py)
+    from plotly.io import templates
+    templates._default = "plotly"

packages/python/plotly/test_init/README.md

@@ -0,0 +1,12 @@
+The test_init test the plotly.py initialization logic and must be run individually.
+
+For example, run...
+```
+$ pytest test_init/test_lazy_imports.py
+$ pytest test_init/test_dependencies_not_imported.py
+``` 
+
+instead of ...
+```
+$ pytest test_init
+``` 

packages/python/plotly/test_init/__init__.py

@@ -0,0 +1,6 @@
+import sys
+import pytest
+
+version_skip = pytest.mark.skipif(
+    sys.version_info < (3, 7), reason="Python version < 3.7"
+)

packages/python/plotly/test_init/test_dependencies_not_imported.py

@@ -0,0 +1,33 @@
+import sys
+from . import version_skip
+
+
+@version_skip
+def test_dependencies_not_imported():
+
+    # Check that creating a figure without using numpy and pandas does not result in
+    # the import of numpy and pandas, even if they are installed.
+    assert 'plotly' not in sys.modules
+    assert 'numpy' not in sys.modules
+    assert 'pandas' not in sys.modules
+
+    import plotly.graph_objects as go
+    fig = go.Figure().add_scatter(x=[0], y=[1])
+    fig.to_json()
+
+    assert 'plotly' in sys.modules
+    assert 'numpy' not in sys.modules
+    assert 'pandas' not in sys.modules
+
+    # check that numpy is installed
+    import numpy as np
+    fig = go.Figure().add_scatter(x=np.array([0]), y=np.array([1]))
+    fig.to_json()
+    assert 'numpy' in sys.modules
+    assert 'pandas' not in sys.modules
+
+    # check that pandas is installed
+    import pandas as pd
+    fig = go.Figure().add_scatter(x=pd.Series([0]), y=pd.Series([1]))
+    fig.to_json()
+    assert 'pandas' in sys.modules

packages/python/plotly/test_init/test_lazy_imports.py

@@ -0,0 +1,38 @@
+import sys
+from . import version_skip
+
+
+@version_skip
+def test_lazy_imports():
+
+    # plotly not imported yet
+    assert 'plotly' not in sys.modules
+
+    # Import top-level plotly module
+    import plotly
+    assert 'plotly' in sys.modules
+
+    # Check that submodules are not auto-imported, but can be be accessed using
+    # attribute syntax
+    submodules = ['graph_objs', 'io', 'express']
+    for m in submodules:
+        module_str = 'plotly.' + m
+        assert module_str not in sys.modules
+
+        getattr(plotly, m)
+        assert module_str in sys.modules
+
+    # Check that constructing and serializing empty figure doesn't auto-import
+    # nested graph objects
+    plotly.graph_objects.Figure().to_json()
+    submodules = [('layout', 'title'), ('scatter', 'marker'), ('scattergl', 'marker')]
+    for module_parts in submodules:
+        module_str = 'plotly.graph_objs.' + '.'.join(module_parts)
+        assert module_str not in sys.modules
+
+        # Use getattr to
+        module = plotly.graph_objects
+        for m in module_parts:
+            module = getattr(module, m)
+
+        assert module_str in sys.modules

packages/python/plotly/tox.ini

@@ -98,6 +98,8 @@ basepython={env:PLOTLY_TOX_PYTHON_37:}
 commands=
     python --version
     pytest {posargs} -x plotly/tests/test_core
+    pytest {posargs} -x test_init/test_dependencies_not_imported.py
+    pytest {posargs} -x test_init/test_lazy_imports.py
 
 ; OPTIONAL ENVIRONMENTS
 ;[testenv:py27-optional]