python2.7 等长梯度切割字符串

现有 1.txt 文本文档，文档内有字符串，如下：
atggcgtttctgctttcattcggaactgaggtgcgggacgagctgcggcgcaactgggga
如何通过python代码（python2.7 等长梯度切割字符串
从第一个字符开始，每次移动一个字符，连续切分成长度为30的字符串，切分后的字符串集合如下，输出到 1qf.txt 文档内（输入输出通过文档进行是关键）

atggcgtttctgctttcattcggaactgag
tggcgtttctgctttcattcggaactgagg
ggcgtttctgctttcattcggaactgaggt
gcgtttctgctttcattcggaactgaggtg
cgtttctgctttcattcggaactgaggtgc
gtttctgctttcattcggaactgaggtgcg
tttctgctttcattcggaactgaggtgcgg
ttctgctttcattcggaactgaggtgcggg
tctgctttcattcggaactgaggtgcggga
ctgctttcattcggaactgaggtgcgggac
tgctttcattcggaactgaggtgcgggacg
gctttcattcggaactgaggtgcgggacga
ctttcattcggaactgaggtgcgggacgag
tttcattcggaactgaggtgcgggacgagc
ttcattcggaactgaggtgcgggacgagct
tcattcggaactgaggtgcgggacgagctg
cattcggaactgaggtgcgggacgagctgc
attcggaactgaggtgcgggacgagctgcg
ttcggaactgaggtgcgggacgagctgcgg
tcggaactgaggtgcgggacgagctgcggc
cggaactgaggtgcgggacgagctgcggcg
ggaactgaggtgcgggacgagctgcggcgc
gaactgaggtgcgggacgagctgcggcgca
aactgaggtgcgggacgagctgcggcgcaa
actgaggtgcgggacgagctgcggcgcaac
ctgaggtgcgggacgagctgcggcgcaact
tgaggtgcgggacgagctgcggcgcaactg
gaggtgcgggacgagctgcggcgcaactgg
aggtgcgggacgagctgcggcgcaactggg
ggtgcgggacgagctgcggcgcaactgggg
gtgcgggacgagctgcggcgcaactgggga

文件读写看上一个程序，关键代码

 s = "atggcgtttctgctttcattcggaactgaggtgcgggacgagctgcggcgcaactgggga"
for i in range(len(s) - 30)
    print(s[i:30])

如果两个问题采纳了，可以给你完整的程序。

正告楼下抄袭本人回答的无耻之徒，本人坚持投诉到底，直到封号为止！

 import sys

file_name = '1.txt'
f = open(file_name)
f1 = open(r"1qf.txt", "a+")
line = f.readline()
for i in range(len(line) - 30 + 1):
    print(line[i:30 + i])
    f1.write(line[i:30 + i] + '\n')
f.close()
f1.close()

1.txt
atggcgtttctgctttcattcggaactgaggtgcgggacgagctgcggcgcaactgggga
1qf.txt
atggcgtttctgctttcattcggaactgag
tggcgtttctgctttcattcggaactgagg
ggcgtttctgctttcattcggaactgaggt
gcgtttctgctttcattcggaactgaggtg
cgtttctgctttcattcggaactgaggtgc
gtttctgctttcattcggaactgaggtgcg
tttctgctttcattcggaactgaggtgcgg
ttctgctttcattcggaactgaggtgcggg
tctgctttcattcggaactgaggtgcggga
ctgctttcattcggaactgaggtgcgggac
tgctttcattcggaactgaggtgcgggacg
gctttcattcggaactgaggtgcgggacga
ctttcattcggaactgaggtgcgggacgag
tttcattcggaactgaggtgcgggacgagc
ttcattcggaactgaggtgcgggacgagct
tcattcggaactgaggtgcgggacgagctg
cattcggaactgaggtgcgggacgagctgc
attcggaactgaggtgcgggacgagctgcg
ttcggaactgaggtgcgggacgagctgcgg
tcggaactgaggtgcgggacgagctgcggc
cggaactgaggtgcgggacgagctgcggcg
ggaactgaggtgcgggacgagctgcggcgc
gaactgaggtgcgggacgagctgcggcgca
aactgaggtgcgggacgagctgcggcgcaa
actgaggtgcgggacgagctgcggcgcaac
ctgaggtgcgggacgagctgcggcgcaact
tgaggtgcgggacgagctgcggcgcaactg
gaggtgcgggacgagctgcggcgcaactgg
aggtgcgggacgagctgcggcgcaactggg
ggtgcgggacgagctgcggcgcaactgggg
gtgcgggacgagctgcggcgcaactgggga

程序经上机验证。这是截图