add local authority data utility functions

functions for:
* matching council name to local authority code
* adding region and county based on local authority code
* adding gss code based on local authority code
* adding type, mapit code etc

These all take a pandas dataframe as an argument and return the same.

src/data_common/local_authority/__init__.py

@@ -0,0 +1,115 @@
+from os.path import join
+import pandas as pd
+
+from ..dataset import get_dataset_df
+
+def fix_council_name(council: str) -> str:
+    return (
+        council.replace("council", "")
+        .replace(" - unitary", "")
+        .replace("(unitary)", "")
+        .strip()
+    )
+
+def add_local_authority_code(df: pd.DataFrame) -> pd.DataFrame:
+    """
+    Add the local-authority-code to the dataframe
+    """
+
+    name_to_code = get_dataset_df(
+        repo="uk_local_authority_names_and_codes",
+        package="uk_la_past_current",
+        version="1",
+        file="lookup_name_to_registry.csv",
+    )
+    df["council_lower"] = df["council"].str.lower().apply(fix_council_name)
+    name_to_code["council_lower"] = (
+        name_to_code["la-name"].str.lower().apply(fix_council_name)
+    )
+    df = df.merge(name_to_code, on="council_lower", how="left")
+
+    # local-authority-code is in last position, move it to the start of the dataframe
+    cols = list(df.columns)
+    cols.insert(0, cols.pop(-1))
+    df = df[cols]
+    df = df.drop(columns=["council_lower", "la-name"])
+    return df
+
+def add_region_and_county(df: pd.DataFrame) -> pd.DataFrame:
+    name_to_code = get_dataset_df(
+        repo="uk_local_authority_names_and_codes",
+        package="uk_la_past_current",
+        version="1",
+        file="uk_local_authorities_current.csv",
+    )
+
+    rows = len(df["council"])
+    df["region"] = pd.Series([None] * rows, index=df.index)
+    df["county"] = pd.Series([None] * rows, index=df.index)
+
+    for index, row in df.iterrows():
+        authority_code = row["local-authority-code"]
+        if not pd.isnull(authority_code):
+            authority_match = name_to_code[
+                name_to_code["local-authority-code"] == authority_code
+            ]
+            df.at[index, "region"] = authority_match["region"].values[0]
+            df.at[index, "county"] = authority_match["county-la"].values[0]
+
+    return df
+
+
+def add_gss_codes(df: pd.DataFrame) -> pd.DataFrame:
+    name_to_code = get_dataset_df(
+        repo="uk_local_authority_names_and_codes",
+        package="uk_la_past_current",
+        version="1",
+        file="uk_local_authorities_current.csv",
+    )
+
+    rows = len(df["council"])
+    df["gss_code"] = pd.Series([None] * rows, index=df.index)
+
+    for index, row in df.iterrows():
+        authority_code = row["local-authority-code"]
+        if not pd.isnull(authority_code):
+            authority_match = name_to_code[
+                name_to_code["local-authority-code"] == authority_code
+            ]
+            df.at[index, "gss_code"] = name_to_code["gss-code"].values[0]
+
+    return df
+
+
+def add_extra_authority_info(df: pd.DataFrame) -> pd.DataFrame:
+    name_to_code = get_dataset_df(
+        repo="uk_local_authority_names_and_codes",
+        package="uk_la_past_current",
+        version="1",
+        file="uk_local_authorities_current.csv",
+    )
+
+    extra_df = name_to_code[
+        [
+            "local-authority-code",
+            "local-authority-type",
+            "wdtk-id",
+            "mapit-area-code",
+            "nation",
+            "gss-code",
+        ]
+    ]
+
+    # the info sheet may contain updated version of columns previously
+    # loaded to sheet, need to drop them before the merge
+    # ignore errors in case columns are not present
+    columns_to_drop = [x for x in extra_df.columns if x != "local-authority-code"]
+    df = df.drop(columns=columns_to_drop, errors="ignore")
+
+    # merge two dataframes using the authority_code as the common reference
+    extra_df = extra_df.merge(df, on="local-authority-code", how="left")
+
+    is_non_english = extra_df["nation"].isin(["Wales", "Scotland", "Northern Ireland"])
+    extra_df.loc[is_non_english, "local-authority-type"] = "UA"
+
+    return extra_df