Python read next()

Question

next() in python does not work. What is an alternative to reading next line in Python? Here is a sample:

filne = "D:/testtube/testdkanimfilternode.txt"
f = open(filne, 'r+')

while 1:
    lines = f.readlines()
    if not lines:
        break
    for line in lines:
        print line
        if (line[:5] == "anim "):
            print 'next() '
            ne = f.next()
            print ' ne ',ne,'\n'
            break

f.close()

Running this on a file does not show 'ne '.

Answer 1

When you do : f.readlines() you already read all the file so f.tell() will show you that you are in the end of the file, and doing f.next() will result in a StopIteration error.

Alternative of what you want to do is:

filne = "D:/testtube/testdkanimfilternode.txt"

with open(filne, 'r+') as f:
    for line in f:
        if line.startswith("anim "):
            print f.next() 
            # Or use next(f, '') to return <empty string> instead of raising a  
            # StopIteration if the last line is also a match.
            break

Answer 2

next() does not work in your case because you first call readlines() which basically sets the file iterator to point to the end of file.

Since you are reading in all the lines anyway you can refer to the next line using an index:

filne = "in"
with open(filne, 'r+') as f:
    lines = f.readlines()
    for i in range(0, len(lines)):
        line = lines[i]
        print line
        if line[:5] == "anim ":
            ne = lines[i + 1] # you may want to check that i < len(lines)
            print ' ne ',ne,'\n'
            break