add CSV utility functions

* get google sheet as a csv
* replace headers in a csv file

Both of these write out a CSV file as the result.

src/data_common/csv/__init__.py

@@ -0,0 +1,31 @@
+import requests
+import urllib3
+
+import pandas as pd
+
+import ssl
+
+ssl._create_default_https_context = ssl._create_unverified_context
+urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
+
+
+def get_google_sheet_as_csv(key, outfile, sheet_name=None):
+    sheet_url = f"https://docs.google.com/spreadsheets/d/{key}/gviz/tq?tqx=out:csv"
+    if sheet_name is not None:
+        sheet_url = f"{sheet_url}&sheet={sheet_name}"
+    r = requests.get(sheet_url)
+
+    with open(outfile, "wb") as outfile:
+        outfile.write(r.content)
+
+
+def replace_csv_headers(csv_file, new_headers, drop_empty_columns=True, outfile=None):
+    if outfile is None:
+        outfile = csv_file
+
+    df = pd.read_csv(csv_file)
+    if drop_empty_columns:
+        df = df.dropna(axis="columns", how="all")
+
+    df.columns = new_headers
+    df.to_csv(open(outfile, "w"), index=False, header=True)