df.ix[df.type==7, ['var1001', 'var1002']] = 0
If you're doing it on all columns, you can just do df.ix[df.type==7] = 0. Or of course if you have a list of the columns whose values you want to replace, you can pass that list in the second slot:
columnsToReplace = ['var1001', 'var1002', ...]
df.ix[df.type==8, columnsToReplace] = 0
