本文实例讲述了Python实现简单过滤文本段的方法。分享给大家供大家参考，具体如下：

一、问题：

如下文本：

## Alignment 0: score=397.0 e_value=8.2e-18 N=9 scaffold1&scaffold106 minus 0- 0: 10026549 10007782 2e-75 0- 1: 10026550 10007781 8e-150 0- 2: 10026552 10007780 1e-116 0- 3: 10026555 10007778 0 0- 4: 10026570 10007768 0 0- 5: 10026579 10007758 4e-15 0- 6: 10026581 10007738 2e-44 0- 7: 10026587 10007734 9e-145 0- 8: 10026591 10007732 2e-147## Alignment 1: score=2304.0 e_value=1e-164 N=47 scaffold1&scaffold107 minus 1- 0: 10026836 10007942 2e-84 1- 1: 10026839 10007940 0 1- 2: 10026840 10007938 0 1- 3: 10026842 10007937 9e-82 1- 4: 10026843 10007935 7e-79 1- 5: 10026847 10007933 3e-119 1- 6: 10026850 10007932 2e-87 1- 7: 10026854 10007928 5e-22 1- 8: 10026855 10007927 3e-101 1- 9: 10026856 10007925 1e-106 1- 10: 10026857 10007924 0 1- 11: 10026858 10007922 9e-123 1- 12: 10026859 10007921 1e-80 1- 13: 10026860 10007920 8e-104 1- 14: 10026862 10007918 4e-25 1- 15: 10026863 10007917 0 1- 16: 10026864 10007912 4e-40 1- 17: 10026865 10007911 0 1- 18: 10026866 10007910 7e-122 1- 19: 10026867 10007908 2e-25 1- 20: 10026868 10007907 0 1- 21: 10026869 10007905 0 1- 22: 10026870 10007904 3e-150 1- 23: 10026871 10007903 5e-77 1- 24: 10026874 10007901 0 1- 25: 10026875 10007897 0 1- 26: 10026876 10007896 0 1- 27: 10026877 10007894 0 1- 28: 10026880 10007893 3e-52 1- 29: 10026881 10007892 0 1- 30: 10026882 10007891 0 1- 31: 10026883 10007890 0 1- 32: 10026886 10007889 1e-50 1- 33: 10026887 10007888 6e-157 1- 34: 10026888 10007887 0 1- 35: 10026889 10007884 0 1- 36: 10026890 10007883 2e-18 1- 37: 10026891 10007882 9e-64 1- 38: 10026892 10007881 0 1- 39: 10026895 10007880 0 1- 40: 10026898 10007875 0 1- 41: 10026900 10007874 0 1- 42: 10026901 10007873 0 1- 43: 10026902 10007871 2e-123 1- 44: 10026903 10007870 0 1- 45: 10026905 10007869 0 1- 46: 10026909 10007868 1e-81## Alignment 2: score=811.0 e_value=3.3e-43 N=17 scaffold1&scaffold111 minus 2- 0: 10026595 10007449 6e-40 2- 1: 10026599 10007448 4e-90 2- 2: 10026600 10007447 0 2- 3: 10026601 10007444 9e-55 2- 4: 10026603 10007438 4e-78 2- 5: 10026604 10007434 9e-122 2- 6: 10026606 10007432 2e-162 2- 7: 10026607 10007427 0 2- 8: 10026608 10007426 0 2- 9: 10026612 10007417 0 2- 10: 10026613 10007415 8e-128 2- 11: 10026614 10007414 3e-64 2- 12: 10026615 10007409 0 2- 13: 10026616 10007406 0 2- 14: 10026617 10007403 1e-171 2- 15: 10026618 10007402 0 2- 16: 10026619 10007397 7e-18........

要求：如果Alignment后面少于20行，把整个的去掉

二、实现方法：

python代码：

#!/usr/bin/pythonsum = 0sumdata = []FD = open("/root/data.txt","r")line = FD.readline()while line: if line.find("Alignment") == 3: if sum >= 20: for i in sumdata: print i, sum=0 sumdata=[line] else: sum = sum + 1 sumdata.append(line) line=FD.readline() if len(line) == 0: if sum >= 20: for i in sumdata: print i,

附：

perl代码

#!/usr/bin/perlopen(FD,"/root/data.txt");while (){ if ($_ =~ /Alignment/){ if($sum >= 20){ print @sumdata;} $sum=0; @sumdata=($_);} else{ $sum++; push(@sumdata,$_);}}print @sumdata if $sum >=20;close(FD);

更多关于Python相关内容感兴趣的读者可查看本站专题：《Python数据结构与算法教程》、《Python函数使用技巧总结》、《Python字符串操作技巧汇总》、《Python入门与进阶经典教程》及《Python文件与目录操作技巧汇总》

希望本文所述对大家Python程序设计有所帮助。