Calculate every other column

Python Help
1

I need to calculate every other column (B columns). It needs to multiply the previous column (A) with column Col2, so Col2 * A1=B1 and then Col2 * A2=B2 and then Col2 * A3=B3

Col1 Col2 Col3 A1 B1 A2 B2 A3 C3
2 5 10 8 9
5 2 10 2 4
9 3 27 8 3

for i in range(df.shape[1], 4, -1):
(df[‘Col2)’]*df[i]-1).round(decimals=1)

This is not working for me. Is there another way to loop through?

2

maybe,

x = pd.DataFrame({'Col2': [2, 5, 9], 'A1': [5, 2, 3], 'B1': [0, 0, 0],
                  'A2': [8, 2, 8], 'B2': [0, 0, 0]})
for i, j in zip(('A1', 'A2'), ('B1', 'B2')):
  x[j] = getattr(x, i) * x.Col2