User  Item
Louis    1
Louis    2
Adam     1
Adam     3

1  2  3
1   0  1  1
2   1  0  0
3   1  0  0

import pandas as pd
import numpy as np
from scipy.sparse import csr_matrix, lil_matrix
raw = pd.DataFrame(columns=['user','item'])
raw['user']=['Louis','Louis','Adam','Adam']
raw['item']=[1,2,1,3]

item_list = raw.item.unique().tolist()
user_list = raw.user.unique().tolist()
m = lil_matrix((len(raw.item.unique()),len(raw.item.unique())))
for user in user_list:
    temp = raw.loc[np.in1d(raw['user'], user)].item
    if len(temp) > 1:
        for idx1, id1 in enumerate(temp[0:-1]):
            for id2 in temp[idx1+1:]:
                m[item_list.index(id1),item_list.index(id2)]+=1
                m[item_list.index(id2),item_list.index(id1)]+=1
m.toarray()