Pandas not taking columns as loc that it just took code example

Example 1: dataframe all companies except

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: dataframe all companies except

>>> df

          a         b         c         d
0  0.175127  0.191051  0.382122  0.869242
1  0.414376  0.300502  0.554819  0.497524
2  0.142878  0.406830  0.314240  0.093132
3  0.337368  0.851783  0.933441  0.949598

>>> df.drop('b', axis=1)

          a         c         d
0  0.175127  0.382122  0.869242
1  0.414376  0.554819  0.497524
2  0.142878  0.314240  0.093132
3  0.337368  0.933441  0.949598