Move scipy import in clearsky.py

docs/sphinx/source/whatsnew/v0.1.0.txt

@@ -40,6 +40,9 @@ Other changes
 * Adding logging calls, removing print calls.
 * Improved PEP8 compliance.
 * Added ``/pvlib/data`` for lookup tables, test, and tutorial data.
+* Limited the scope of ``clearsky.py``'s ``scipy`` dependency.
+  ``clearsky.ineichen`` will work without ``scipy`` so long as 
+  the Linke Turbidity is supplied as a keyword argument. (:issue:`13`)
 * Removed NREL's SPA code to comply with their license (:issue:`9`).
 
 
@@ -56,7 +59,7 @@ Documentation
 Testing
 ~~~~~~~
 
-* Tests are cleaner and more thorough. They are still no where near complete.
+* Tests are cleaner and more thorough. They are still nowhere near complete.
 * Using Coveralls to measure test coverage. 
 * Using TravisCI for automated testing.
 * Using ``nosetests`` for more concise test code. 

pvlib/clearsky.py

@@ -12,7 +12,6 @@
 
 import numpy as np
 import pandas as pd
-import scipy.io
 
 from pvlib import tools
 from pvlib import irradiance
@@ -127,9 +126,17 @@ def ineichen(time, location, linke_turbidity=None,
         # so divide the number from the file by 20 to get the
         # turbidity.
 
+        try:
+            import scipy.io
+        except ImportError:
+            raise ImportError('The Linke turbidity lookup table requires scipy. ' +
+                              'You can still use clearsky.ineichen if you ' +
+                              'supply your own turbidities.')
+
         # consider putting this code at module level
         this_path = os.path.dirname(os.path.abspath(__file__))
         logger.debug('this_path={}'.format(this_path))
+
         mat = scipy.io.loadmat(os.path.join(this_path, 'data', 'LinkeTurbidities.mat'))
         linke_turbidity = mat['LinkeTurbidity']
         LatitudeIndex = np.round_(_linearly_scale(location.latitude,90,- 90,1,2160))

pvlib/test/test_clearsky.py

@@ -30,18 +30,19 @@
 
 def test_ineichen_required():
     # the clearsky function should lookup the linke turbidity on its own
+    # will fail without scipy
     clearsky.ineichen(times, tus)
 
 def test_ineichen_supply_linke():
     clearsky.ineichen(times, tus, linke_turbidity=3)
 
 def test_ineichen_solpos():
     clearsky.ineichen(times, tus, linke_turbidity=3,
-                            solarposition_method='pyephem')
+                      solarposition_method='pyephem')
 
 def test_ineichen_airmass():
     clearsky.ineichen(times, tus, linke_turbidity=3,
-                            airmass_model='simple')
+                      airmass_model='simple')
 
 def test_ineichen_keys():
     clearsky_data = clearsky.ineichen(times, tus, linke_turbidity=3)
@@ -60,7 +61,7 @@ def test_haurwitz_keys():
 
 # test DISC
 def test_disc_keys():
-    clearsky_data = clearsky.ineichen(times, tus)
+    clearsky_data = clearsky.ineichen(times, tus, linke_turbidity=3)
     disc_data = clearsky.disc(clearsky_data['GHI'], ephem_data['zenith'], 
                               ephem_data.index)
     assert 'DNI_gen_DISC' in disc_data.columns