Touchstone class save method added

NanoVNASaver/Touchstone.py

@@ -202,3 +202,34 @@ class Touchstone:
                 logger.warning("Reordering data")
                 for datalist in self.sdata:
                     datalist.sort(key=attrgetter("freq"))
+
+    def save(self, nr_params: int = 1):
+        """Save touchstone data to file.
+
+        Args:
+            nr_params: Number of s-parameters. 2 for s1p, 4 for s2p
+        """
+
+        logger.info("Attempting to open file %s for writing",
+                    self.filename)
+        with open(self.filename, "w") as outfile:
+            outfile.write(self.saves(nr_params))
+
+    def saves(self, nr_params: int = 1  ) -> str:
+        """Returns touchstone data as string.
+
+        Args:
+            nr_params: Number of s-parameters. 1 for s1p, 4 for s2p
+        """
+        assert nr_params in (1, 4)
+
+        ts_str = "# HZ S RI R 50\n"
+        for i, dp_s11 in enumerate(self.s11data):
+            ts_str += f"{dp_s11.freq} {dp_s11.re} {dp_s11.im}"
+            for j in range(1, nr_params):
+                dp = self.sdata[j][i]
+                if dp.freq != dp_s11.freq:
+                    raise LookupError("Frequencies of sdata not correlated")
+                ts_str +=f" {dp.re} {dp.im}"
+            ts_str += "\n"
+        return ts_str

test/data/broken_pair.s1p

@@ -1,9 +0,0 @@
-# Hz S RI R 50
-140000000 -0.720544874 -0.074467673
-140307234 -0.707615315 -0.045678697
-140614468 -0.694235622 -0.017205553
-140921702 -0.679476678 0.011064857
-141228936  0.037949264
-141536169 -0.645231842 0.06495472
-141843404 -0.625548779 0.090901531
-142150638 -0.605278372 0.116493001

test/data/broken_pair.s2p

@@ -0,0 +1,10 @@
+! Vector Network Analyzer VNA R2
+! Tucson Amateur Packet Radio
+! Saturday, 9 November, 2019   17:48:47
+! Frequency              S11                           S21                            S12                            S22
+! ListType=Lin
+# HZ  S  RI R 50
+000500000    -3.33238E-001  1.80018E-004    6.74780E-001  -8.19510E-007    6.75290E-001  -8.20129E-007    -3.33238E-001  
+001382728    -3.33017E-001  6.89580E-004    6.74251E-001  -3.70855E-004    6.74761E-001  -5.04361E-004    -3.33016E-001  9.45694E-004
+002265456    -3.33136E-001  1.06095E-003    6.74766E-001  -1.00228E-003    6.75276E-001  -1.00304E-003    -3.33136E-001  1.06095E-003
+003148184    -3.33120E-001  1.97467E-003    6.74773E-001  -1.65230E-003    6.74773E-001  -1.65230E-003    -3.33121E-001  1.91064E-003

test/test_touchstone.py

@@ -16,10 +16,11 @@
 #  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 import unittest
 import logging
+import os
 
 # Import targets to be tested
 from NanoVNASaver.Touchstone import Options, Touchstone
-
+from NanoVNASaver.RFTools import Datapoint
 
 class TestTouchstoneOptions(unittest.TestCase):
     def setUp(self):
@@ -81,6 +82,21 @@ class TestTouchstoneTouchstone(unittest.TestCase):
         ts.load()
         self.assertEqual(str(ts.opts), "# HZ S DB R 50")
 
+        ts = Touchstone("./test/data/broken_pair.s2p")
+        with self.assertLogs(level=logging.ERROR) as cm:
+            ts.load()
+        self.assertRegex(cm.output[0], "Data values aren't pairs")
+
+        ts = Touchstone("./test/data/missing_pair.s2p")
+        with self.assertLogs(level=logging.ERROR) as cm:
+            ts.load()
+        self.assertRegex(cm.output[0], "Inconsistent number")
+
+        ts = Touchstone("./test/data/nonexistent.s2p")
+        with self.assertLogs(level=logging.ERROR) as cm:
+            ts.load()
+        self.assertRegex(cm.output[0], "No such file or directory")
+
     def test_db_conversation(self):
         ts_db = Touchstone("./test/data/attenuator-0643_DB.s2p")
         ts_db.load()
@@ -111,3 +127,26 @@ class TestTouchstoneTouchstone(unittest.TestCase):
         self.assertIn("!freq ReS11 ImS11 ReS21 ImS21 ReS12 ImS12 ReS22 ImS22",
                       ts.comments)
 
+    def test_save(self):
+        ts = Touchstone("./test/data/valid.s2p")
+        self.assertEqual(ts.saves(), "# HZ S RI R 50\n")
+        ts.load()
+        lines = ts.saves().splitlines()
+        self.assertEqual(len(lines), 1021)
+        self.assertEqual(lines[0], "# HZ S RI R 50")
+        self.assertEqual(lines[1], '500000 -0.333238 0.000180018')
+        self.assertEqual(lines[-1], '900000000 -0.127646 0.31969')
+        lines = ts.saves(4).splitlines()
+        self.assertEqual(len(lines), 1021)
+        self.assertEqual(lines[0], "# HZ S RI R 50")
+        self.assertEqual(lines[1], '500000 -0.333238 0.000180018 0.67478 -8.1951e-07 0.67529 -8.20129e-07 -0.333238 0.000308078')
+        self.assertEqual(lines[-1], '900000000 -0.127646 0.31969 0.596287 -0.503453 0.599076 -0.50197 -0.122713 0.326965')
+        ts.filename = "./test/data/output.s2p"
+        ts.save(4)
+        os.remove(ts.filename)
+        ts.filename = ""
+        self.assertRaises(FileNotFoundError, ts.save)
+
+        ts.s11data[0] = Datapoint(100, 0.1, 0.1)
+        self.assertRaisesRegex(
+            LookupError, "Frequencies of sdata not correlated", ts.saves, 4)