Python newbie needs file I/O help

[donchoi]

Hi, newbie here, sorry. I have a couple of basic Python questions.

1) How do I open 'datafile' and skip to the ith line for reading? I have a loop counter i for this purpose. The data file is very long, and I'd like to read just 100 lines in at a time or so.

2) Is there any easy way to determine the length of a text file (in lines) besides opening the file, reading each line and using a counter?

[donchoi]

Never mind, I think I just found a way around my problem. Better algorithm means I don't need to do this anymore. Thanks!

[bartonc]

Hi, newbie here, sorry. I have a couple of basic Python questions.

1) How do I open 'datafile' and skip to the ith line for reading? I have a loop counter i for this purpose. The data file is very long, and I'd like to read just 100 lines in at a time or so.

2) Is there any easy way to determine the length of a text file (in lines) besides opening the file, reading each line and using a counter?

For future reference, file.readlines( ) returns a Python list object. So:

f = open("fileName")
linesList = f.readlines()
f.close()
nLines = len(linesList)
nth = 5
nthLine = linesList[nth]

[ghostdog74]

for very large files, you might want to iterate through the file

...
for num,line in enumerate(open("file")):
     if num == 9:
         print "skip line 10"
     #do+something