[英]How to write to a specific line in file in Python?
我有一个文件作为格式:
xxxxx
yyyyy
zzzzz
ttttt
我需要在xxxxx和yyyyy行之间写文件:
xxxxx
my_line
yyyyyy
zzzzz
ttttt
with open('input') as fin, open('output','w') as fout:
for line in fin:
fout.write(line)
if line == 'xxxxx\n':
next_line = next(fin)
if next_line == 'yyyyy\n':
fout.write('my_line\n')
fout.write(next_line)
这会将您的行插入文件中每次出现的xxxxx\\n
和yyyyy\\n
。
另一种方法是编写一个函数以产生行,直到看到xxxxx\\nyyyyy\\n
def getlines(fobj,line1,line2):
for line in iter(fobj.readline,''): #This is necessary to get `fobj.tell` to work
yield line
if line == line1:
pos = fobj.tell()
next_line = next(fobj):
fobj.seek(pos)
if next_line == line2:
return
然后,您可以使用此传递的内容直接写入writelines
:
with open('input') as fin, open('output','w') as fout:
fout.writelines(getlines(fin,'xxxxx\n','yyyyy\n'))
fout.write('my_line\n')
fout.writelines(fin)
如果文件很小,则可以简单地使用str.replace()
:
>>> !cat abc.txt
xxxxx
yyyyy
zzzzz
ttttt
>>> with open("abc.txt") as f,open("out.txt",'w') as o:
data=f.read()
data=data.replace("xxxxx\nyyyyy","xxxxx\nyourline\nyyyyy")
o.write(data)
....:
>>> !cat out.txt
xxxxx
yourline
yyyyy
zzzzz
ttttt
对于大型文件,请使用mgilson的方法。
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