Use a bool variable to indicate whether an optional module is available

Author: seisman

pygmt/datasets/tile_map.py

@@ -5,8 +5,10 @@
 
 try:
     import contextily
+
+    _has_contextily = True
 except ImportError:
-    contextily = None
+    _has_contextily = False
 
 import numpy as np
 import xarray as xr
@@ -108,7 +110,7 @@ def load_tile_map(region, zoom="auto", source=None, lonlat=True, wait=0, max_ret
       * x            (x) float64 -2.004e+07 -1.996e+07 ... 1.996e+07 2.004e+07
     """
     # pylint: disable=too-many-locals
-    if contextily is None:
+    if not _has_contextily:
         raise ImportError(
             "Package `contextily` is required to be installed to use this function. "
             "Please use `python -m pip install contextily` or "

pygmt/figure.py

@@ -8,8 +8,10 @@
 
 try:
     import IPython
+
+    _has_ipython = True
 except ImportError:
-    IPython = None  # pylint: disable=invalid-name
+    _has_ipython = False
 
 
 from pygmt.clib import Session
@@ -33,7 +35,7 @@
 }
 
 # Show figures in Jupyter notebooks if available
-if IPython:
+if _has_ipython:
     get_ipython = IPython.get_ipython()  # pylint: disable=invalid-name
     if get_ipython and "IPKernelApp" in get_ipython.config:  # Jupyter Notebook enabled
         SHOW_CONFIG["method"] = "notebook"
@@ -452,7 +454,7 @@ def show(self, dpi=300, width=500, method=None, waiting=0.5, **kwargs):
             )
 
         if method == "notebook":
-            if IPython is None:
+            if not _has_ipython:
                 raise GMTError(
                     "Notebook display is selected, but IPython is not available. "
                     "Make sure you have IPython installed, "

pygmt/src/tilemap.py

@@ -7,8 +7,10 @@
 
 try:
     import rioxarray
+
+    _has_rioxarray = True
 except ImportError:
-    rioxarray = None
+    _has_rioxarray = False
 
 
 @fmt_docstring
@@ -114,7 +116,7 @@ def tilemap(
     """
     kwargs = self._preprocess(**kwargs)  # pylint: disable=protected-access
 
-    if rioxarray is None:
+    if not _has_rioxarray:
         raise ImportError(
             "Package `rioxarray` is required to be installed to use this function. "
             "Please use `python -m pip install rioxarray` or "

pygmt/tests/test_figure.py

@@ -8,8 +8,10 @@
 
 try:
     import IPython
+
+    _has_ipython = True
 except ImportError:
-    IPython = None  # pylint: disable=invalid-name
+    _has_ipython = False
 
 
 import numpy as np
@@ -313,7 +315,7 @@ def test_figure_savefig_worldfile():
                 fig.savefig(fname=imgfile.name, worldfile=True)
 
 
-@pytest.mark.skipif(IPython is None, reason="run when IPython is installed")
+@pytest.mark.skipif(not _has_ipython, reason="run when IPython is installed")
 def test_figure_show():
     """
     Test that show creates the correct file name and deletes the temp dir.
@@ -354,7 +356,7 @@ def test_figure_show_invalid_method():
         fig.show(method="test")
 
 
-@pytest.mark.skipif(IPython is not None, reason="run without IPython installed")
+@pytest.mark.skipif(_has_ipython, reason="run without IPython installed")
 def test_figure_show_notebook_error_without_ipython():
     """
     Test to check if an error is raised when display method is 'notebook', but