How to write if else statement when column value is null - python pandas

Daily I am loading some files. Each file is loading into 2 tables based on some filters. For example Table1.C1 column values is null python script must go to second Table script. cursor.execute("update Fact StagingTable1 set Is_Active=0 where C1 = ?", C1) At the above line script is failing when C1 is null.

How to write the code? Please help me.

This is the original script I used

import os, sys, time
import glob
import shutil
import os
import pandas as pd
import time
import numpy as np
import pyodbc 

todaysdate = time.strftime("%Y%m%d")

folder_name ="C:\\Path"
dest =  "C:\\Path\\Archive\\"
file_type = ''
#all_Sales_files = sorted(glob.glob(folder_name + "/*Sales_*" ))
#all_Sales_files_sorted=sorted(os.listdir(folder_name))
file_titles = ['Col1']
os.chdir(folder_name)
all_Sales_files = filter(os.path.isfile, os.listdir(folder_name))
all_Sales_files = [os.path.join(folder_name, filename) for filename in all_Sales_files] # add path to each file
all_Sales_files.sort(key=lambda x: os.path.getmtime(x))

for filename in all_Sales_files:
    base = os.path.basename(filename)
    basewoe = os.path.splitext(base)[0]
    print(base + " File is started processing ...")

## File1 is processing into Table1  base on conditions
    df=pd.read_csv(filename, header=None,names=file_titles,low_memory=False)

    sql_conn = pyodbc.connect(
    "Driver={SQL Server};"
    "Server=DB_Server;"
    "Database=DB;"
    "Trusted_Connection=yes;")
    cursor = sql_conn.cursor()
    cursor.execute("truncate table StagingTable1")
    print(base +':   truncate staging table StagingTable1 is successful...')
    print(base +':   Data is started loading into staging table StagingTable1....')  

    for index,row in dfd.iterrows():
        cursor.execute("INSERT INTO StagingTable1(C1,C2) Values (?,?)",
    row['C1'],
    row['C2'],

                  )
    sql_conn.commit()
    print(base +':   Data Loading into staging table StagingTable1 is successful...')
    cursor.close()
    sql_conn.close()

    C1=cursor.execute("select top 1 C1 from StagingTable1")
    C1_Result = cursor.fetchall()
    C1=[]
    for C1 in C1_Result:
        print(C1)
    cursor.execute("update Fact StagingTable1 set Is_Active=0 where C1 = ?", C1)
    sql_insert_query = "insert into FactTable1 select * from StagingTable1"
    cursor.execute(sql_insert_query)
    sql_conn.commit()

## File1 is processing into Table2 base on conditions

    df=pd.read_csv(filename, header=None,names=file_titles,low_memory=False)

    sql_conn = pyodbc.connect(
    "Driver={SQL Server};"
    "Server=DB_Server;"
    "Database=DB;"
    "Trusted_Connection=yes;")
    cursor = sql_conn.cursor()
    cursor.execute("truncate table StagingTable1")
    print(base +':   truncate staging table StagingTable1 is successful...')
    print(base +':   Data is started loading into staging table StagingTable1....')  
    for index,row in dfd.iterrows():
        cursor.execute("INSERT INTO StagingTable2 (C1,C2) Values (?,?)",
    row['C1'],
    row['C2'],
                  )
    sql_conn.commit()
    print(base +':   Data Loading into staging table StagingTable2 is successful...')
    cursor.close()
    sql_conn.close()
    print(base +':   Data Loading into table Fact table Fact StagingTable2 is started...')
    sql_insert_query = "insert into FactTable2 select * from StagingTable2"
    cursor.execute(sql_insert_query)
    sql_conn.commit()
    shutil.move(filename, dest)
    print("Archiving "+ base +" file is successful...")
print("All files of Sales are successfully loaded into tables...")