allow import with no fits reader installed

.travis.yml

@@ -3,22 +3,24 @@ language: python
 # Setting sudo to false opts in to Travis-CI container-based builds.
 sudo: false
 
-python:
-    - 2.7
-    - 3.5
-
 env:
     global:
-        - NUMPY_VERSION=1.11
+        - PYTHON_VERSION=3.6
+        - NUMPY_VERSION=1.12
         - CMD='./test.py'
         - COVERAGE=0
         - EXTRAS='fitsio'
 
 matrix:
     include:
-        # test without fitsio installed.
-        - python: 3.5
-          env: CMD='./test.py --cov-report= --cov=sfdmap' COVERAGE=1 EXTRAS=''
+        - env: PYTHON_VERSION=3.4 NUMPY_VERSION=1.11
+        - env: PYTHON_VERSION=2.7
+        - env: PYTHON_VERSION=2.7 EXTRAS='astropy'
+
+        # test with astropy instead of fitsio installed.
+        - env: CMD='./test.py --cov-report= --cov=sfdmap' COVERAGE=1 EXTRAS='astropy'
+        # test that import works with no FITS reader installed.
+        - env: EXTRAS=''
 
 before_install:
     - wget http://repo.continuum.io/miniconda/Miniconda-latest-Linux-x86_64.sh -O miniconda.sh
@@ -30,7 +32,7 @@ before_install:
 # Note: leave numpy in all `conda install` commands to prevent conda from
 # upgrading it automatically.
 install:
-    - conda create -c openastronomy --yes -n test python=$TRAVIS_PYTHON_VERSION numpy=$NUMPY_VERSION astropy pytest $EXTRAS
+    - conda create -c openastronomy --yes -n test python=$PYTHON_VERSION numpy=$NUMPY_VERSION $EXTRAS pytest
     - source activate test
     - if [[ $COVERAGE ]]; then pip install pytest-cov coveralls; fi
     - source activate test

sfdmap.py

@@ -1,5 +1,7 @@
 # Licensed under an MIT "Expat" license - See LICENSE
-"""Get E(B-V) values from the Schlegel, Finkbeiner & Davis (1998) dust map."""
+"""Get E(B-V) values from the Schlegel, Finkbeiner & Davis (1998) dust map.
+
+Dust maps must be downloaded separately."""
 
 import os
 
@@ -13,15 +15,20 @@
     try:
         from astropy.io.fits import getdata
     except ImportError:
-        raise ImportError("could not import fitsio or astropy.io.fits")
+        # If we don't have either reader, raise an error only when the function
+        # is called. This is so that we can import the module with just numpy
+        # installed (the minimum dependency).
+        def getdata(*args, **kwargs):
+            raise ImportError("Could not import fitsio or astropy.io.fits. "
+                              "Install fitsio or astropy.")
+
 
 __all__ = ['SFDMap', 'ebv']
 __version__ = "0.1.0"
 
 
 def _isiterable(obj):
     """Returns `True` if the given object is iterable."""
-
     try:
         iter(obj)
         return True

test.py

@@ -4,16 +4,28 @@
 
 import numpy as np
 from numpy.testing import assert_allclose
-from astropy.coordinates import SkyCoord
 import pytest
-
+try:
+    from astropy.coordinates import SkyCoord
+    HAVE_ASTROPY = True
+except ImportError:
+    HAVE_ASTROPY = False
+try:
+    import fitsio
+    HAVE_FITSIO = True
+except:
+    HAVE_FITSIO = False
+
 import sfdmap
 
-# -----------------------------------------------------------------------------
-# Test coordinate conversions
 
-import os
+# We end up skipping most of the tests if we don't have a FITS reader
+# but we want to be able to run them anyway to test that importing works
+# with minimal dependencies (numpy).
+HAVE_FITS_READER = HAVE_FITSIO or HAVE_ASTROPY
 
+# -----------------------------------------------------------------------------
+# Test coordinate conversions
 
 datapath = os.path.join(os.path.dirname(__file__), "testdata")
 TOL = 0.0001  # tolerance in arcseconds
@@ -111,6 +123,8 @@ def test_bilinear_interpolate():
 MINIMAP_SFD = sfdmap.SFDMap('testdata', north='SFD_dust_4096_ngp_cutout.fits',
                             scaling=1.0)
 
+
+@pytest.mark.skipif(not HAVE_FITS_READER, reason="no FITS reader")
 def test_versus_ned():
     """Test versus NED results"""
 
@@ -125,7 +139,8 @@ def test_versus_ned():
         ebv = MINIMAP_SFD.ebv(d['ra'], d['dec'])
         assert_allclose(ebv, d['ebv'], rtol=0.0, atol=0.001)
 
-
+
+@pytest.mark.skipif(not HAVE_FITS_READER, reason="no FITS reader")    
 def test_array_inputs():
     """Test array inputs (values from NED test above)."""
     ra = np.array([204.17470, 205.40142])
@@ -134,6 +149,7 @@ def test_array_inputs():
     assert_allclose(ebv, [0.077315, 0.0539752], rtol=0.0, atol=0.001)
 
 
+@pytest.mark.skipif(not HAVE_ASTROPY, reason="no astropy")
 def test_skycoord():
     """Test that skycoord gives same results"""
 
@@ -144,7 +160,7 @@ def test_skycoord():
 
 
 # only test locally when we have the full images.
-@pytest.mark.skipif("SFD_DIR" not in os.environ,
+@pytest.mark.skipif("SFD_DIR" not in os.environ or not HAVE_FITS_READER,
                     reason="SFD_DIR environment variable not set")
 def test_boundaries():
     """Test that interpolation=False works at b=0"""
@@ -162,6 +178,7 @@ def test_repr():
     assert "SFDMap(" in s
 
 
+@pytest.mark.skipif(not HAVE_FITS_READER, reason="no FITS reader")
 def test_convenience_func():
     ebv1 = MINIMAP.ebv(204.0, -30.0)
     ebv2 = sfdmap.ebv(204.0, -30.0, mapdir='testdata',
@@ -170,6 +187,7 @@ def test_convenience_func():
     assert ebv1 == ebv2
 
 
+@pytest.mark.skipif(not HAVE_FITS_READER, reason="no FITS reader")
 def test_interpolate_false():
     """Test no interpolation (also tests fk5j2000)."""
     # position off-center of a pixel, but reference value is pixel value.
@@ -178,12 +196,14 @@ def test_interpolate_false():
     assert_allclose(ebv, 0.0552888, atol=0.0000001, rtol=0.0)
 
 
+@pytest.mark.skipif(not HAVE_FITS_READER, reason="no FITS reader")
 def test_tuple_arg():
     """Test that passing (ra, dec) as a tuple works."""
 
     assert MINIMAP.ebv(204.0, -30.0) == MINIMAP.ebv((204.0, -30.0))
 
 
+@pytest.mark.skipif(not HAVE_FITS_READER, reason="no FITS reader")
 def test_argument_exceptions():
     """Test wrong numbers or types of arguments"""
 
@@ -197,6 +217,7 @@ def test_argument_exceptions():
         MINIMAP.ebv(0., 0., 0.)
 
 
+@pytest.mark.skipif(not HAVE_FITS_READER, reason="no FITS reader")
 def test_input_options():
     """Test unit and frame options."""