title: convert pandas dataframe datatypes from float64 into int64
body: <p>I am trying to read CSV file by using python pandas, in the resultant dataframe one column is returned as float64 datatype instead of int64. But I could see most of the values are numbers and some of them are null values in the existing CSV file</p>
  
  <pre><code>df = pd.read_csv(file)
  
  dh.head(3)
  
  Name State  Id
  SFO  CA     123.0
  JFK  NY     152.0
  CHG  IL     NaN
  ABC  AZ     NaN
  
  df.dypes
  
  Name Object
  State Object
  Id float64
  </code></pre>
  
  <p>I tried convert Id column into Int64 to upload data into oracle table</p>
  
  <pre><code>df['Id'] = df['Id'].astype('int64')
  </code></pre>
  
  <p>Error : Cannot convert NA to integer</p>
  
  <p>Is there any approach to convert Id column into int64 ? I appreciate your response.</p>