Python Read Next()

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

Solution 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"withopen(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

Solution 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

Solution 3:

lines = f.readlines()

reads all the lines of the file f. So it makes sense that there aren't any more line to read in the file f. If you want to read the file line by line, use readline().

Solution 4:

You don't need to read the next line, you are iterating through the lines. lines is a list (an array), and for line in lines is iterating over it. Every time you are finished with one you move onto the next line. If you want to skip to the next line just continue out of the current loop.

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

lines = f.readlines() # get all lines as a list (array)# Iterate over each line, printing each line and then move to the next
for line in lines:
    print line

f.close()

Solution 5:

A small change to your algorithm:

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

while1:
    lines = f.readlines()
    ifnotlines:
        break
    line_iter= iter(lines) # here
    for line in line_iter: # and here
        print line
        if (line[:5] == "anim "):
            print'next() '
            ne = line_iter.next() # and here
            print' ne ',ne,'\n'break

f.close()

However, using the pairwise function from itertools recipes:

defpairwise(iterable):
    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
    a, b = itertools.tee(iterable)
    next(b, None)
    return itertools.izip(a, b)

you can change your loop into:

for line, next_line in pairwise(f): # iterate over the file directlyprint line
    if line.startswith("anim "):
        print'next() 'print' ne ', next_line, '\n'break