Reading line by line from a file in python

Question

In order to extract some values from this file :

I need to read it line by line. I tried to read line by line first but i don't know why it doesn't work.

I tried this :

#! /usr/bin/python
file = open('/home/results/err.txt')
for line in file.readline():
    print line

EDIT:

Problem: working but not showing this lines (this is the file)

Just the last line of them which is: (this is what is generated)

If there is another unrelated problem, post it as a separate question, instead of editing this one. Also please include text as text instead of screenshots. — mkrieger1, Aug 17 '17 at 15:56

spencer · Answer 1 · 2017-08-17T15:44:48.067

2

You might want to use a context manager with that to automatically close your opened file after the lines have been read, that is to ensure nothing unexpected happens to your file while python is processing it.

with open('/home/results/err.txt', 'r') as file:
for line in file:
    print line

readline() would read your file line-by-line but iterating over that would print the letters individually.

edited Aug 17 '17 at 15:44

answered Aug 17 '17 at 15:36

spencer

179
10

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thank you it resolves the problem but had another problem, i write it in the edit – c.ceti Aug 17 '17 at 15:44

score 1 · Accepted Answer · answered Aug 17 '17 at 15:30

1

You need to iterate through the file rather than the line:

#! /usr/bin/python
file = open('/home/results/err.txt')
for line in file:
    print line

file.readline() only reads the first line. When you iterate over it, you are iterating over the characters in the line.

answered Aug 17 '17 at 15:30

Sumner Evans

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thank you it resolves the problem but had another problem, i write it in the edit – c.ceti Aug 17 '17 at 15:44
@c.ceti, it looks like you have different files. The contents of the lines are entirely different. – Sumner Evans Aug 17 '17 at 15:48
It's a long file actually, what i made as first picture is its beginning and the other picture is the middle – c.ceti Aug 17 '17 at 15:50

score 1 · Answer 3 · answered Aug 17 '17 at 15:30

1

file.readline() already reads one line. Iterating over that line gives you the individual characters.

Instead, use:

for line in file:
    …

answered Aug 17 '17 at 15:30

mkrieger1

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thank you it resolves the problem but had another problem, i write it in the edit – c.ceti Aug 17 '17 at 15:46

score 1 · Answer 4 · answered Aug 17 '17 at 15:31

1

Try this :

#! /usr/bin/python
file = open('/home/results/err.txt')
for line in file.readlines():
    print line

answered Aug 17 '17 at 15:31

OzOm18

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1
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`file.readlines` will read the file line by line – OzOm18 Aug 17 '17 at 15:33
Why comment when you can improve your answer ? – NatNgs Aug 17 '17 at 15:39
didn't think about it. My bad :-) – OzOm18 Aug 17 '17 at 15:45
thank you it resolves the problem but had another problem, i write it in the edit – c.ceti Aug 17 '17 at 15:46
am not getting the other problem. – OzOm18 Aug 17 '17 at 15:50

Reading line by line from a file in python

4 Answers4