Allow read_surfrad to parse http files

docs/sphinx/source/whatsnew/v0.9.2.rst

@@ -8,6 +8,9 @@ Deprecations
 
 Enhancements
 ~~~~~~~~~~~~
+* :py:func:`pvlib.iotools.read_surfrad` now also accepts remote files
+  with https links in addition to files on the SURFRAD FTP server
+  (:pull:`1459`)
 * Add :py:func:`pvlib.tracking.calc_surface_orientation` for calculating
   single-axis tracker ``surface_tilt`` and ``surface_azimuth`` from
   rotation angles. (:issue:`1471`, :pull:`1480`)
@@ -47,8 +50,9 @@ Requirements
 
 Contributors
 ~~~~~~~~~~~~
+* Adam R. Jensen (:ghuser:`AdamRJensen`)
 * Naman Priyadarshi (:ghuser:`Naman-Priyadarshi`)
 * Chencheng Luo (:ghuser:`roger-lcc`)
 * Prajwal Borkar (:ghuser:`PrajwalBorkar`) 
 * Kevin Anderson (:ghuser:`kanderso-nrel`)
-* Cliff Hansen (:ghuser:`cwhanse`)
+* Cliff Hansen (:ghuser:`cwhanse`)

pvlib/iotools/surfrad.py

@@ -44,7 +44,7 @@ def read_surfrad(filename, map_variables=True):
     Parameters
     ----------
     filename: str
-        Filepath or url.
+        Filepath or URL. URL can be either FTP or HTTP.
     map_variables: bool
         When true, renames columns of the Dataframe to pvlib variable names
         where applicable. See variable :const:`VARIABLE_MAP`.
@@ -113,7 +113,8 @@ def read_surfrad(filename, map_variables=True):
     =======================  ======  ==========================================
 
     See README files located in the station directories in the SURFRAD
-    data archives [2]_ for details on SURFRAD daily data files.
+    data archives [2]_ for details on SURFRAD daily data files. In addition to
+    the FTP server, the SURFRAD files are also available via HTTP access [3]_.
 
     References
     ----------
@@ -122,8 +123,10 @@ def read_surfrad(filename, map_variables=True):
        `SURFRAD Homepage <https://www.esrl.noaa.gov/gmd/grad/surfrad/>`_
     .. [2] NOAA SURFRAD Data Archive
        `SURFRAD Archive <ftp://aftp.cmdl.noaa.gov/data/radiation/surfrad/>`_
+    .. [3] `NOAA SURFRAD HTTP Index
+       <https://gml.noaa.gov/aftp/data/radiation/surfrad/>`_
     """
-    if str(filename).startswith('ftp'):
+    if str(filename).startswith('ftp') or str(filename).startswith('http'):
         req = Request(filename)
         response = urlopen(req)
         file_buffer = io.StringIO(response.read().decode(errors='ignore'))

pvlib/tests/iotools/test_surfrad.py

@@ -7,6 +7,8 @@
 testfile = DATA_DIR / 'surfrad-slv16001.dat'
 network_testfile = ('ftp://aftp.cmdl.noaa.gov/data/radiation/surfrad/'
                     'Alamosa_CO/2016/slv16001.dat')
+https_testfile = ('https://gml.noaa.gov/aftp/data/radiation/surfrad/'
+                  'Alamosa_CO/2016/slv16001.dat')
 
 
 @pytest.mark.remote_data
@@ -19,6 +21,17 @@ def test_read_surfrad_network():
     assert local_data.equals(network_data)
 
 
+@pytest.mark.remote_data
+@pytest.mark.flaky(reruns=RERUNS, reruns_delay=RERUNS_DELAY)
+def test_read_surfrad_https():
+    # Test reading of https files.
+    # If this test begins failing, SURFRAD's data structure or data
+    # archive may have changed.
+    local_data, _ = surfrad.read_surfrad(testfile)
+    network_data, _ = surfrad.read_surfrad(https_testfile)
+    assert local_data.equals(network_data)
+
+
 def test_read_surfrad_columns_no_map():
     data, _ = surfrad.read_surfrad(testfile, map_variables=False)
     assert 'zen' in data.columns