New Step.time property

It offers a more robust way of accesing the time of a snapshot if
time series data are missing.

Author: amorison

stagpy/_step.py

@@ -519,7 +519,22 @@ def geom(self):
     @property
     def timeinfo(self):
         """Time series data of the time step."""
-        return self.sdat.tseries.at_step(self.istep)
+        try:
+            info = self.sdat.tseries.at_step(self.istep)
+        except KeyError:
+            raise error.MissingDataError(f'No time series for {self!r}')
+        return info
+
+    @property
+    def time(self):
+        """Time of this time step."""
+        steptime = None
+        try:
+            steptime = self.timeinfo['t']
+        except error.MissingDataError:
+            if self.isnap is not None:
+                steptime = self.geom.ti_ad
+        return steptime
 
     @property
     def isnap(self):

stagpy/stagyydata.py

@@ -487,20 +487,17 @@ def at_time(self, time, after=False):
         Returns:
             :class:`~stagpy._step.Step`: the relevant snap.
         """
-        if self.sdat.tseries is None:
-            return None
-
         # in theory, this could be a valid implementation of _Steps.at_time
         # but this isn't safe against missing data...
         igm = 0
         igp = len(self) - 1
         while igp - igm > 1:
             istart = igm + (igp - igm) // 2
-            if self[istart].timeinfo['t'] >= time:
+            if self[istart].time >= time:
                 igp = istart
             else:
                 igm = istart
-        if self[igp].timeinfo['t'] > time and not after and igp > 0:
+        if self[igp].time > time and not after and igp > 0:
             igp -= 1
         return self[igp]