序列GC含量计算

import string

def Compute_GC (seq):
    GC = 0
    total =0
    for i in range(0, len(seq)):
        if string.upper(seq[i]) in ['A','T','G','C']:
            total = total +1
        if string.upper(seq[i]) in ['G', 'C']:
            GC = GC+1
    return float(GC)/total*100

seq = 'atcgAATTTCCGGGGTTAATCAGNNNtgGT'
print 'GC percent of %s %2.2f%%' % (seq,Compute_GC(seq))