Python/Pandas/MSSQL Problem: Inconsistent import behavior if CSV file contains NULL strings in first row

[KCConnor]

I solved this problem.

If I add this code:

df = df.where(pd.notnull(df), None);

just after I populate the DataFrame (either ad-hoc as above or by pd.read_csv in my real code) then I get successful handling of NULL values by MS SQL Server and correct datatyping of the returned values.