Files, Seek, and Readlines. A newbie question

[John Purser]

Hello,

I'm using a large (>120,000 lines) sorted ASCII text file as an index.  I
started running into problems as soon as I began to use the .seek() to
position before a read.  Even when not opened as a binary file seek moves by
bytes not lines.  Is there a line oriented seek version?  Is there a better
way to get to line 50 than:
myFile.seek(0)
myFile.readlines(49)
Record = myFile.readline()
?

Thanks,

John Purser