The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all() on this "==" operator Python Pandas

I have a script like this

if vms2['STATUS'] == 1:
    vms2['entry']=vms['STATUS']+vms2['status_after']
else :
    vms2['entry']=vms['STATUS']+vms2['status_before']

it shows error like this:

The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

I am new in Python, so I can'f figured the source of the error. Please help.