Python:nested for循环被字典中的空值中断

我对循环和API非常陌生。我目前正在试用IEX的沙箱来收集财务数据。我所做的是收集IEX支持的股票符号列表,然后使用该列表调用数据并将其附加到数据帧中。问题是,有些年IEX没有特定安全性的数据。我希望在数据帧中保持这种安全性,如果缺少值,就写N/A。我的循环代码如下:

my_columns = ['date','Ticker','Price','o_cash_flow','total_income',
          'total_assets','total_liab','rev','ebit','ttm_eps',
          'shares_out','profit_margin','total_rev','2year_return',
          '1year_return','6month_return','3month_return','1month_return']

financials_df = pd.DataFrame(columns = my_columns)

for symbol_string in symbol_strings:
    batch_api_call_url = f'{sandbox_url}/stable/stock/market/batch?symbols={symbol_string}&types=price,financials,stats,advanced-stats&range=2q&token={token}'
    data = requests.get(batch_api_call_url).json()
    for symbol in symbol_string.split(','):
        print(data[symbol])
        financials_df = financials_df.append(
        pd.Series
     [
            data[symbol]['financials']['financials'][0]['fiscalDate'],
            symbol,
            data[symbol]['price'],
            data[symbol]['financials']['financials'][0]['cashFlow'],
            data[symbol]['financials']['financials'][0]['netIncome'],
            data[symbol]['financials']['financials'][0]['totalAssets'],
            data[symbol]['financials']['financials'][0]['totalLiabilities'],
            data[symbol]['financials']['financials'][0]['revenue'],
            data[symbol]['financials']['financials'][0]['ebit'],
            data[symbol]['stats']['ttmEPS'],
            data[symbol]['stats']['sharesOutstanding'],
            data[symbol]['advanced-stats']['profitMargin'],
            data[symbol]['advanced-stats']['totalRevenue'],
            data[symbol]['stats']['year2ChangePercent'],
            data[symbol]['stats']['year1ChangePercent'],
            data[symbol]['stats']['month6ChangePercent'],
            data[symbol]['stats']['month3ChangePercent'],
            data[symbol]['stats']['month1ChangePercent']
    ],
        index = my_columns),
            ignore_index = True
        )

然后,我收到一个错误“KeyError:‘financials’”,这是因为某些证券缺少第二次调用financials。我希望循环只在dataframe中用N/A替换数据,并在发生这种情况时继续从api调用数据。任何帮助都将不胜感激,谢谢。