How to select the last column of dataframe

Use iloc and select all rows (:) against the last column (-1):

df.iloc[:,-1:]

These are few things which will help you in understanding everything... using iloc

In iloc, [initial row:ending row, initial column:ending column]

case 1: if you want only last column --- df.iloc[:,-1] & df.iloc[:,-1:] this means that you want only the last column...

case 2: if you want all columns and all rows except the last column --- df.iloc[:,:-1] this means that you want all columns and all rows except the last column...

case 3: if you want only last row --- df.iloc[-1:,:] & df.iloc[-1,:] this means that you want only the last row...

case 4: if you want all columns and all rows except the last row --- df.iloc[:-1,:] this means that you want all columns and all rows except the last column...

case 5: if you want all columns and all rows except the last row and last column --- df.iloc[:-1,:-1] this means that you want all columns and all rows except the last column and last row...

Somewhat similar to your original attempt, but more Pythonic, is to use Python's standard negative-indexing convention to count backwards from the end:

df[df.columns[-1]]