assigning values to column in pandas data-frame based on if condition

I have a column A, which has values Y and N. I want to assign 1 for Y and 0 of N, using the if condition in python. The following code throws an error: ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

if df1[df1['A']=='Y']:
    df1['A']=1
else:
    df1['A']=0