def findreplace_prefix_cols(df, old_prefix, new_prefix):
    """List columns names with old prefix replaced by new prefix."""
    sel = [colname.startswith(old_prefix) for colname in df.columns]
    old_cols = df.columns[sel]
    new_cols = [old_col.replace(old_prefix, new_prefix, 1)
                for old_col in old_cols]
    return new_cols