Editing particular lines of a text file.

[Shriphani]

Hello all,

I am trying to create a script that looks at specific strings in a
file like:

msgid "I am a disco dancer."

and compares the part in quotes to the keys in a dictionary, finds the
value and creates a new line right after this string in the file. I
have planned to write this as follows:

1. Open the file in read mode
2. parse each line to figure out which line contains "msgid" and use
the shlex module's split method to go and split this line and pick the
2nd element list[1].
3. find the value from the dictionary corresponding to the above
element.
4. Insert the line. This part is where I face a problem. How do I
plainly edit just one line. I would also like to look at some sample
code that does this.
5. open a new file and write the new file with the inserted strings to
it.
6. close both files opened.

Regards,
Shriphani Palakodety