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:

Expand|Select|Wrap|Line Numbers

 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

Expand|Select|Wrap|Line Numbers

 
...

for num,line in enumerate(open("file")):

     if num == 9:

         print "skip line 10"

     #do+something

Python newbie needs file I/O help

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