Question

More details below:

1st line

2nd line

3rd line

4th line

...

Now want to insert a new line named zero line before 1st line. File looks like below:

zero line

1st line

2nd line

3rd line

4th line

...

I know sed command can do this work, but how to do it using python? Thanks

Answer 1

you can use fileinput

>>> import fileinput
>>> for linenum,line in enumerate( fileinput.FileInput("file",inplace=1) ):
...   if linenum==0 :
...     print "new line"
...     print line.rstrip()
...   else:
...     print line.rstrip()
...