[Tutor] counting elements in list

kumar s ps_python at yahoo.com
Wed Sep 15 19:14:02 CEST 2010

Hi group:

I have a list:

 k = ['T', 'C', 'T', 'T', 'T', 'T', 'T', 'T', 'T', 'C', 'T', 'T', 'T', 'C', 'T', 
'T', 'T', 'C', 'C', 'T', 'T', 'T', 'C', 'T', 'T', 'T', 'T', 'T', 'T']

the allowed elements are A or T or G or C. List can have any number of A or T or 
G or C

My aim is to get a string ouput with counts of each type A or T or G or C.  


from the above example, I could count T and C and since there are no A and G, I 
want to print 0 for them. I just dont know how this can be done. 

>>> d = {}
>>> for i in set(k):
...     d[i] = k.count(i)
>>> d
{'C': 6, 'T': 23}

>>> for keys,values in d.items():
...     print keys+'\t'+str(d[keys])
C       6
T       23

the other way i tried is:
>>> k.count('A'),k.count('T'),k.count('G'),k.count('C')
(0, 23, 0, 6)

 how can I get counts for those elements not represented in list and print 
them.  appreciate your help. 



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