title: How to force Pandas to read numbers as "int64" instead of "float64"
body: <p>I have an issue where all of the legacy code I have written no longer works.</p>
  
  <p>I have pandas reading an Excel file, and instead of reading as int64, it now reads as float64.  It is an issue because I cannot perform .merge or .isin on different data type.  I know I can use df.blah.astype(int), but that is very inconvenient to refactor and seems like it should not be necessary.</p>
  
  <p>I am not sure what has caused this.  I am working on a new build of Windows 10, Python 3.5, and Pandas 18.1.  All that changed was an upgrade from Windows 7 and Pandas 18.0.</p>
  
  <p>Was there any change to Pandas?  I cannot find any change in the release notes.</p>
  
  <p>Thanks for any help!</p>