open read and close a file in 1 line of code

Question

Now I use:

pageHeadSectionFile = open(\'pagehead.section.htm\',\'r\')
output = pageHeadSectionFile.read()
pageHeadSectionFile.close()

But t

Answer 1

You don't really have to close it - Python will do it automatically either during garbage collection or at program exit. But as @delnan noted, it's better practice to explicitly close it for various reasons.

So, what you can do to keep it short, simple and explicit:

with open('pagehead.section.htm','r') as f:
    output = f.read()

Now it's just two lines and pretty readable, I think.

Answer 2

Using more_itertools.with_iter, it is possible to open, read, close and assign an equivalent output in one line (excluding the import statement):

import more_itertools as mit


output = "".join(line for line in mit.with_iter(open("pagehead.section.htm", "r")))

Although possible, I would look for another approach other than assigning the contents of a file to a variable, i.e. lazy iteration - this can be done using a traditional with block or in the example above by removing join() and iterating output.

Answer 3

use ilio: (inline io):

just one function call instead of file open(), read(), close().

from ilio import read

content = read('filename')

Answer 4

What you can do is to use the with statement, and write the two steps on one line:

>>> with open('pagehead.section.htm', 'r') as fin: output = fin.read();
>>> print(output)
some content

The with statement will take care to call __exit__ function of the given object even if something bad happened in your code; it's close to the try... finally syntax. For object returned by open, __exit__ corresponds to file closure.

This statement has been introduced with Python 2.6.

Answer 5

I frequently do something like this when I need to get a few lines surrounding something I've grepped in a log file:

$ grep -n "xlrd" requirements.txt | awk -F ":" '{print $1}'
54

$ python -c "with open('requirements.txt') as file: print ''.join(file.readlines()[52:55])"
wsgiref==0.1.2
xlrd==0.9.2
xlwt==0.7.5