Python DataFrame Replace values of specific conditions with nan

I read the data from Panda through pd.read_csv.

pd = pd.read_csv('data.csv')
data= pd['header']

There's a zero in the read value has zero I want to give the value of 0 in nan. So,

data = data.replace(0,np.NAN)

If you give it, 0 changes to nan.

But I want to talk about no negative numbers I added conditions after reloading the data.

data= pd['header']
data = data.replace(0<data , np.NAN)

There is no error, but it does not change. That's all I'm saying

data[data<0] = 'nan'

If you do that, the nano value will be str.

Is there a way?