通常從測序公司拿到的fq文件分為四行，第一行為序列名稱，第二行為序列的堿基，第三行為序列名稱，通常用+號(hào)代替，第四行為堿基質(zhì)量。
代碼如下：

from collections import Counter
with open('srg1.r1.paired.fq','r') as Fileout, open('srg1.r1.paired.results.txt','w') as Filein:
  i = 4
  dic, arr = {}, []
  while True:
      line = Fileout.readline()
      i += 1
      if i%4 == 2:
          arr.append(len(str(line)))
      if not line:
          break
  dic = Counter(arr)
  for k,v in dic.iteritems():
       Filein.write(k + v)

shell:

cat your.fq | paste ----| awk '{print ">"$1 "\n" $2}'