Read a File 8 Lines at a Time Python

Question

Hello I am trying to read a file in Python 8 lines at a time and use the current 8 lines as str variables

However I am unable to do this correctly and would appreciate any help

with open("test.txt", 'r') as infile:
    lines_gen = islice(infile, 8)
    for lines in lines_gen:
        firstname = str(lines[0])
        lastname = str(lines[1])
        email = str(lines[2])

...

How can I achieve this

*cheers

And ty for any help

what's the content of `test.txt`? – Ashwini Chaudhary Dec 17 '12 at 06:14 — Ashwini Chaudhary, Dec 17 '12 at 06:14
What is the error you are getting? – Abhijit Dec 17 '12 at 06:17 — Abhijit, Dec 17 '12 at 06:17

John La Rooy · Answer 1 · 2012-12-17T06:34:34.750

3

Using the usual n things at a time pattern

from itertools import izip

with open("test.txt") as f:
    line_gen = izip(*[f]*8)
    for lines in line_gen:
        print lines
        firstname, lastname, email, fourth, fifth, sixth, seventh, eighth = lines
        ...

edited Dec 17 '12 at 06:34

answered Dec 17 '12 at 06:26

John La Rooy

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Himanshu · Answer 2 · 2012-12-17T06:37:59.897

2

How about this :-

with open("test.txt", 'r') as infile:
    lines_gen = infile.readlines()
    for i in range(0, len(lines_gen), 8):
        (firstname, lastname, email, etc1, ..) = lines_gen[i:i+8]

untested

edited Dec 17 '12 at 06:37

answered Dec 17 '12 at 06:16

Himanshu

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`len()` on an iterator? `len(lines_gen)`. – Ashwini Chaudhary Dec 17 '12 at 06:19
still wrong, the variable `lines` will raise `NameError`. And `islice() `based solution would be better here as using `readlines()` you loaded the whole file into memory. – Ashwini Chaudhary Dec 17 '12 at 06:25
Ok this seemed to solve what I needed after changing lines[i:i+8] to lines_gen[i:i+8] don't know if that is accurate but seems to work ty – townlong Dec 17 '12 at 06:37

Abhijit · Accepted Answer · 2012-12-17T06:48:16.807

2

A simple implementation using itertools.islice

from itertools import islice
with open("test.txt") as fin:
    try:
        while True:
            data =  islice(fin, 0, 8)

            firstname = next(data)
            lastname = next(data)
            email = next(data)
            #.....
    except StopIteration:
        pass

A better more pythonic implementation

>>> from collections import namedtuple
>>> from itertools import islice
>>> records = namedtuple('record',
                  ('firstname','lastname','email' #, .....
               ))
>>> with open("test.txt") as fin:
    try:
        while True:
            data =  islice(fin, 0, 3)

            data = record(*data)
            print data.firstname, data.lastname, data.email #.......
    except (StopIteration, TypeError):
        pass

edited Dec 17 '12 at 06:48

answered Dec 17 '12 at 06:17

Abhijit

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This will result in an infinite loop. – Ashwini Chaudhary Dec 17 '12 at 06:35
@AshwiniChaudhary: Can you think of a scenario which can cause this snippet to be in infinite loop? – Abhijit Dec 17 '12 at 06:38
My bad it was an indentation issue, that's why I was getting different output. +1 – Ashwini Chaudhary Dec 17 '12 at 06:45
@AshwiniChaudhary: I have posted a better Pythonic Solution using namedtuple – Abhijit Dec 17 '12 at 06:48
`firstname,lastname,email,....=[next(data) for _ in range(8)]` will also work fine here. – Ashwini Chaudhary Dec 17 '12 at 06:50

jackcogdill · Answer 4 · 2012-12-17T06:35:08.797

Try this:

every_eight = []
lines = open('test.txt').readlines()
j = 0
for n in range(0, len(lines) +1, 8):
    every_eight.append(''.join([lines[l] for l in range(j, n)]))
    j = n

By the way, if you're trying to accept mass input for tons of people or something, you could try using dictionaires in a list like this:

info = []

every_eight = []
lines = open('test.txt').readlines()
j = 0
for n in range(0, len(lines) +1, 8):
    every_eight.append([lines[l] for l in range(j, n)])
    j = n

for setinf in every_eight:
    if len(setinf) == 8:
        info.append({
                'firstname': setinf[0],
                'lastname' : setinf[1],
                'email'    : setinf[2],
            })

for inf in info:
    print inf

vz0 · Answer 5 · 2012-12-17T06:41:55.890

0

with open("test.txt", 'r') as infile:
    it = iter(infile)
    while True:
        lines_list = []
        try:
            for i in range(8):
                lines_list.append(next(it))
        except StopIteration:
            if len(lines_list) == 0:
                break
        for eight_lines in lines_list:
            # Do something with eight_lines[0:8]

edited Dec 17 '12 at 06:41

answered Dec 17 '12 at 06:33

vz0

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Read a File 8 Lines at a Time Python

5 Answers5