Coerce some columns designated as integer types

wetterdienst/additionals/functions.py

@@ -1,6 +1,7 @@
 """
 A set of more general functions used for the organization
 """
+import pandas as pd
 from typing import Tuple, List, Optional, Union, Callable
 
 from wetterdienst.constants.parameter_mapping import TIME_RESOLUTION_PARAMETER_MAPPING
@@ -219,6 +220,32 @@ def create_station_data_dtype_mapping(columns: List[str]) -> dict:
     return station_data_dtype_mapping
 
 
+def coerce_integer_columns(df: pd.DataFrame):
+    """
+    Coerce columns designated as Integer types.
+
+    :param df:
+    :return:
+    """
+    integer_fields = [
+
+        # Different fields designating quality levels.
+        'QN',
+        'QN_3',
+        'QN_4',
+
+        # "precipitation_form" from "daily observations"
+        'RSKF',
+    ]
+
+    # In version 0.24.+ pandas has gained the ability to hold integer dtypes with missing values.
+    # https://pandas.pydata.org/pandas-docs/stable/user_guide/integer_na.html
+    # https://stackoverflow.com/questions/21287624/convert-pandas-column-containing-nans-to-dtype-int/21290084
+    for integer_field in integer_fields:
+        if integer_field in df.columns:
+            df[integer_field] = df[integer_field].astype('Int64')
+
+
 def cast_to_list(iterable_) -> list:
     """
     A function that either converts an existing iterable to a list or simply puts the item into a list to make an

wetterdienst/parsing_data/parse_data_from_files.py

@@ -6,7 +6,7 @@
 from functools import partial
 from multiprocessing import Pool
 
-from wetterdienst.additionals.functions import create_station_data_dtype_mapping
+from wetterdienst.additionals.functions import create_station_data_dtype_mapping, coerce_integer_columns
 from wetterdienst.constants.column_name_mapping import GERMAN_TO_ENGLISH_COLUMNS_MAPPING
 from wetterdienst.constants.metadata import NA_STRING, STATION_DATA_SEP
 from wetterdienst.enumerations.column_names_enumeration import DWDMetaColumns, DWDOrigColumns
@@ -136,4 +136,7 @@ def _parse_dwd_data(filename_and_file: Tuple[str, BytesIO],
     # Coerce the data types appropriately.
     data = data.astype(create_station_data_dtype_mapping(data.columns))
 
+    # Coerce Integer data types.
+    coerce_integer_columns(data)
+
     return data