File one
dna = "AGTACCGATACATAGCC"
counts = {'A':0, 'T':0, 'C':0, 'G':0}
for b in dna:
if b == 'A':
counts['A'] += 1
elif b == 'C':
counts['C'] += 1
elif b == 'G':
counts['G'] += 1
elif b == 'T':
counts['T'] += 1
counts = {'A':0, 'T':0, 'C':0, 'G':0}
for b in dna:
print 'key is', b,
counts[b] += 1
print 'value is now', counts[b]
print counts
File two
dna = "AGTACCGATNACATAGCC"
#counts = {'A':0, 'T':0, 'C':0, 'G':0}
counts = {}
for b in dna:
if b not in counts:
counts[b] = 0
counts[b] += 1
#for k in counts:
# print k, counts[k]
keys = counts.keys()
keys.sort()
for k in keys:
print k, counts[k]
#print counts.items()