Getting next line in a file

file = open(input,"r").read()
lines =  file.read().splitlines()
for i in range(len(lines)):
     line = lines[i]
     next_line = lines[i+1]

Just loop over the open file:

infile = open(input,"r")
for line in infile:
    line = doSomething(line, next(infile))

Because you now use the file as an iterator, you can call the next() function on the infile variable at any time to retrieve an extra line.

Two extra tips:

Don't call your variable file; it masks the built-in file type object in python. I named it infile instead.
You can use the open file as a context manager with the with statement. It'll close the file for you automatically when done:
```
with open(input,"r") as infile:
    for line in infile:
        line = doSomething(line, next(infile))
```

I think that you mean that if you are in line n, you want to be able to access line n+1.

The simplest way to do that is to replace

for line in file.splitlines():

with

lines = file.readlines()
for i in xrange(len(lines)):

then you can get the current line with lines[i] and the next line with lines[i+1]

the more pythonic way is to use enumerate

lines = file.readlines()
for index, line in enumerate(lines):

now you have the current line in "line" like normal, but you also have the index if you want to find a different line relative to it.

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