Python 从dataframe列检查字符串是否为nan

当我打印

数据['words']时，从数据框中获取值

['from' 'fairest' 'creatures' 'we' 'desire' 'increase' nan 'that' 'thereby']

当我这样循环时，如何识别值是否为nan

for w in data['words'].values:
    check if w is nan ????

使用pandas方法测试：

问题是关于是否：

for i in range(150,160):
  if (pd.isnull(df['Text'][i])):
    print('is null')

或计算所有NaN：

cnt=0
for i in range(len(dframe)):
  if (pd.isnull(dframe['Description'][i])):
    cnt+=1

cnt=0
for i in range(len(dframe)):
  if (pd.isnull(dframe['Description'][i])):
    cnt+=1