how to select all columns except last column in pandas code example

Example 1: pandas select all columns except one

df.loc[:, df.columns != 'b']

          a         c         d
0  0.561196  0.013768  0.772827
1  0.882641  0.615396  0.075381
2  0.368824  0.651378  0.397203
3  0.788730  0.568099  0.869127

Example 2: how to select all but last columns in python

df.iloc[:,:-1]