Add memory usage debug function

chemicals/__init__.py

@@ -186,7 +186,21 @@ def constant_statistics():
                     else:
                         counts[p] = set(prop_CASs)
         return {k: len(v) for k, v in counts.items()}
-
+
+    def memory_usage(finish_loading=True):
+        if finish_loading:
+            complete_lazy_loading()
+        usages = []
+        names = []
+        for name, df in data_reader.df_sources.items():
+            names.append(name)
+            usages.append(df.memory_usage().values.sum())
+
+        names = [x for _, x in sorted(zip(usages, names))]
+        usages.sort()
+        for name, use in zip(names, usages):
+            print(f'{name} : {use/1024**2:3f} MB')
+        print(f'Total usage: {sum(usages)/1024**2:3f} MB')
 
     global vectorized, numba, units, numba_vectorized
     if PY37: