data processing, correlation calculation
Pandas is the best thing since sliced bread (for data science, at least). 

an example:

import pd
In [22]: df = pd.read_csv('yourexample.csv')

In [23]: df
Out[23]:
   user   item1   item2
0     a        2      4
1     b        1      3
2     c        5      6

In [24]: df.columns
Out[24]: Index([u'user ', u'item1 ', u'item2'], dtype='object')

In [25]: df.corr()
Out[25]:
          item1      item2
item1   1.000000  0.995871
item2   0.995871  1.000000

In [26]: df.cov()
Out[26]:
          item1      item2
item1   4.333333  3.166667
item2   3.166667  2.333333


Bingo!