[Tutor] How to create a dictionary for ount elements

[Wolfgang Maier]

On 04.06.2014 12:29, jarod_v6 at libero.it wrote:
> Dear all thanks for your suggestion!!!
>
> In [4]: with open("prova.csv") as p:
>      for i in p:
>          lines =i.rstrip("\n").split("\t")
>          line = (lines[0],lines[1])
>     ...:         diz.setdefault(line,set()).add(lines[2])
>     ...:
>
> In [5]: diz
> Out[5]:
> {('program1', 'sample1'): {'TP53'},
>   ('program1', 'sample2'): {'ATF3', 'PRNP'},
>   ('program2', 'sample1'): {'PRNP', 'TP53'},
>   ('program2', 'sample2'): {'TLK1', 'TRIM32'},
>   ('programs ', 'sample'): {'gene'}}
>
>
> So what I want to do is to use intersect between the keys recursively:
> s = diz[('program2', 'sample1']
>     ....:
>     ....:
> KeyboardInterrupt
>
> In [14]: s = diz[('program2', 'sample1')]
>
> In [15]: s
> Out[15]: {'PRNP', 'TP53'}
>
> In [16]: a
> Out[16]: {'ATF3', 'PRNP'}
>
> In [17]: s.inte
> s.intersection         s.intersection_update
>
> In [17]: s.intersection(a)
> Out[17]: {'PRNP'}
>
> How can Have a intersect of all my dictionary and from ('program1', 'sample1')
> vs ('program1', 'sample2')...
> I want to count  how many genes are common
> Thanks in advance  for your help!
>

So you know the basic method set.intersection (or its operator form &).
The rest depends on which intersections you're interested in.
For all pair-wise comparisons, you can use nested for loops across all 
key, value pairs, like so:
for k1, v1 in your_dict.iteritems():
     for k2, v2 in your_dict.iteritems():
         do_something()

For any kind of systematic comparison, it's probably better to build a 
set of all programs and one of all samples during file parsing, in 
addition to the dict, then use their values for accessing the dict.

Best, Wolfgang