Remove deprecated pandas inplace keyword argument usage

This was done for AOSS Tower, but needs to be done here too. Pandas deprecated the inplace=True behavior, this merge request removes its use.

mendotabuoy/level_b1/nc.py

@@ -47,13 +47,11 @@ def _get_data(input_files, parser):
 
 def get_data(input_files, parser):
     frame = pd.DataFrame(_get_data(input_files, parser))
-    frame.set_index('TIMESTAMP', inplace=True)
+    frame = frame.set_index('TIMESTAMP')
     # XXX: Do we need to check for -999 too?
-    frame.mask(frame == -99999., inplace=True)
-    frame.fillna(value=np.nan, inplace=True)
+    frame = frame.mask(frame == -99999.).fillna(value=np.nan)
     # get rid of unused fields
-    frame.drop(columns=['RECORD', 'OSSignature', 'programversion'],
-               inplace=True)
+    frame = frame.drop(columns=['RECORD', 'OSSignature', 'programversion'])
     return frame
 
 
@@ -184,8 +182,8 @@ def create_giant_netcdf(input_files, output_fn, zlib, chunk_size,
     # drop unused variables
     frame = filter_unused_columns(frame, database)
     # rename columns to netcdf friendly names
-    frame.rename(lambda col_name: db_rename.get(col_name, col_name),
-                 axis='columns', inplace=True)
+    frame = frame.rename(lambda col_name: db_rename.get(col_name, col_name),
+                         axis='columns')
 
     # Add wind direction components so we can average wind direction properly
     frame['wind_east'], frame['wind_north'], _ = calc.wind_vector_components(frame['wind_speed'], frame['wind_dir'])
@@ -218,7 +216,7 @@ def create_giant_netcdf(input_files, output_fn, zlib, chunk_size,
         frame['gust'] = new_frame['gust'].resample(interval_width, closed='right', loffset=interval_width).max()
         del frame['wind_east']
         del frame['wind_north']
-    frame.fillna(np.nan, inplace=True)
+    frame = frame.fillna(np.nan)
 
     if start and end:
         frame = frame[start.strftime('%Y-%m-%d %H:%M:%S'): end.strftime('%Y-%m-%d %H:%M:%S')]
@@ -257,7 +255,7 @@ def create_giant_netcdf(input_files, output_fn, zlib, chunk_size,
     written_vars.extend(write_var(nc_file.variables, depths,
                                   'depth', database, qc=False))
 
-    frame.drop(columns=all_water_depth_deps, inplace=True)
+    frame = frame.drop(columns=all_water_depth_deps)
     written_vars.extend(write_vars(nc_file, frame, database, station_info))
     unwritten_vars = set(nc_file.variables.keys()) - set(written_vars)
     written_vars.extend(write_qc_for_unwritten(nc_file.variables,