Added fromFile() method to overcome problem of multiple times opening same file

python_src/lasp/lasp_measurement.py

@@ -970,6 +970,22 @@ class Measurement:
 
         wavfile.write(fn, int(self.samplerate), data.astype(newtype))
 
+    @staticmethod
+    def fromFile(fn):
+        """
+        Try to open measurement from a given file name. First checks
+        whether the measurement is already open. Otherwise it might
+        happen that a Measurement object is created twice for the same backing file, which we do not allow.
+        """
+        # See if the base part of the filename is referring to a file that is already open
+        with h5.File(fn, 'r') as f:
+            uuid = f.attrs['UUID']
+
+        if uuid in Measurement.uuid_s.keys():
+            return Measurement.uuid_s[uuid]
+        
+        return Measurement(fn)
+
     @staticmethod
     def fromtxt(
         fn,