Timestamp.to_pydatetime() cannot be applied to an entire Series

#### Problem description
When I tried to compare 2 columns of date in one dataframe, if one column has type pandas._libs.tslib.Timestamp while the other is python datetime, a mere comparison will return an error of  `Cannot change data-type for object array.`

To compare, I have to convert Timestamp to datetime. According to the API, I can use the function to_pydatetime(). However, this only works on one Timestamp value, but cannot be applied to the entire column as shown in the screenshot

![image](https://user-images.githubusercontent.com/7760158/50213914-f4a81500-03b9-11e9-8c65-712b8e33ed0e.png)

Is there an alternative solution to this? Thanks