为什么 DF 有时会自动更新，有时不会？

Question

So, I'm unclear why doing certain operations on a DF updates it right away, but other times it does not update it unless you re-use the old name or use a new df variable name.

Doesn't this make it really confusing where the last 'real' change is?

Answer 1

First of all, a df behaves like a list in python, meaning that if you make a soft copy of it and change it, the original df changes too. To answer your question you must know that some methods of updating a df, write on a hard copy version of that df (which are indicated by a warning given by pandas letting you know that you are writing on a copy) so the data might not change. the best and most reliable way to change data using pandas is either:

df.at[a_cell] = some_data

or:

df.loc[some_rows, some_columns] = some_data