QST: Events generated when dataframes are changed
- [x ] I have searched the [[pandas] tag](https://stackoverflow.com/questions/tagged/pandas) on StackOverflow for similar questions.

- [x ] I have asked my usage related question on [StackOverflow](https://stackoverflow.com).

here is a link to this question (similar) 
https://stackoverflow.com/questions/48209811/how-to-notify-pandas-dataframe-modification


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#### Question about pandas

What events are generated when a dataframe is updated in pandas? for example if a column is dropped or a value is changed in a cell? I am not interested in accesses, but I'd like to know if a dataframe in my environment goes away or if it is altered. 

