pandas: compute % change between 2 columns, without rounding

Question

I want to compute the percentage change in value between 2 columns like below

df['change' ] =100*(df[df.columns[1]]-df[df.columns[0]])/df[df.columns[0]]

However I noted when the change values are very small like 0.001, Python round them to 0.

I want the exact values. Thank you