Python: Opening a file within a print() function

Question

I am aware that when you open a file in Python, you must always close it. However, I was wondering what happens if you're not assigning your file to a variable and are only opening it in a print function.

Example: print(open('file.txt','r').read())

Is there a way to close a file opened within a function?

Something more pythonic than

F=open('file.txt','r')
print(F.read())
F.close()

Trying to do a bunch of stuff in one line is not Pythonic. Don't try to open the file inside the `print` call. — BrenBarn, Aug 21 '15 at 20:31
Why? That's not "Pythonic" at all, it's just a bad idea and hard to read. — Morgan Thrapp, Aug 21 '15 at 20:32
In Python3.5, you can: print(pathlib.Path('file.txt').read_text()) — Veky, Oct 12 '15 at 13:04

score 2 · Accepted Answer · answered Aug 21 '15 at 20:33

2

Use the with construct.

with open('file.txt', 'r') as f:
    print(f.read())

If the file is very large, I suggest iterating over it and printing it a line at a time:

with open('file.txt', 'r') as f:
    for line in f:
        print(line, end='')

Of course, if the file is that large, it's probably not useful to print it to an ordinary console, but this practice is very useful for processing large files.

answered Aug 21 '15 at 20:33

TigerhawkT3

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Wait, so this would close it automatically right? – Oleg Silkin Aug 21 '15 at 20:47
Yes, that's right. As soon as the `with` block ends, the file is closed, regardless of any errors that may have occurred. – TigerhawkT3 Aug 21 '15 at 20:49

score 1 · Answer 2 · answered Aug 21 '15 at 20:32

1

So opening a file like that is not a good idea.

Just use context managers:

with open('file.txt','r') as f:
    print(f.read())

answered Aug 21 '15 at 20:32

bcollins

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This is much better, thank you – Oleg Silkin Aug 21 '15 at 20:32

Python: Opening a file within a print() function

2 Answers2