Adjust postprocessing example and add Hands-on

lectures/debugging-strategies/slides.qmd

@@ -310,7 +310,7 @@ $\Rightarrow$_Show use of `gdb`_
  
 # Errors due to data access and communication
 
-## Postprocessing example (1/3)
+## Postprocessing example (1/4)
 
  - Extract data from netCDF file and calculate interpolation weights
  - File located [here](static/vmro3_input4MIPs_ozone_1850-1855_rev.nc)
@@ -326,7 +326,7 @@ Calculate_Weights(filename, timestamp_start, timestamp_end, timestep_days)
 ```
 
 
-## Postprocessing example (2/3)
+## Postprocessing example (2/4)
 
 :::{.smaller}
 
@@ -358,7 +358,7 @@ def Calculate_Weights(filename, timestamp_start, timestamp_end, timestep_days):
 :::
 
 
-## Postprocessing example (3/3)
+## Postprocessing example (3/4)
 
 
 ```python
@@ -376,7 +376,31 @@ def Select_Date(ds, model_date, method):
         '%Y-%m-%d %H:%M:%S')
 ```
 
-:::{.fragment}
+<!--
+```python
+def Open_File(filename):
+    import xarray as xr
+
+    return xr.open_dataset(filename)\
+        .convert_calendar('standard', use_cftime=True)
+
+def Select_Date(ds, model_date, method='ffill'):
+    import datetime as dt
+
+    if ( model_date < dt.datetime(1850, 1, 16, 12, 0, 0) ) \
+        or ( model_date > dt.datetime(1854, 12, 31, 12, 0, 0) ):
+        ds_elem = ds.sel(time=model_date, method='nearest')
+    else :
+        ds_elem = ds.sel(time=model_date, method=method)
+
+    return dt.datetime.strptime(str(ds_elem['time'].values),
+        '%Y-%m-%d %H:%M:%S')
+```
+-->
+
+
+## Postprocessing example (4/4)
+
 
 ```{.python startFrom="14"}
 def Get_Time_Objects(timestamp_start, timestamp_end, timestep_days):
@@ -389,8 +413,19 @@ def Get_Time_Objects(timestamp_start, timestamp_end, timestep_days):
     return [start_date, end_date, timestep]
 ```
 
-:::
 
+## Hands-On! {.handson}
+
+1. Which command in the code causes the problem?
+2. Describe what would you need to do?
+   (you can inspect the data e.g. with `print(ds['time'])`
+   or in your terminal with `cdo infon <file>.nc`)
+
+<!--
+```
+ncdump -h
+```
+-->
 
 ## Parallel programs