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For this video, we'll continue 
with our read_poem code.  | www.downloadly.ir

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Before we make any changes, have a look at line 7.
This closes the file, and is very important. 

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If you don't close a file when you're finished 
with it, you could run out of file handles. 

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File handles (or file descriptors, on Mac 
and Linux) are used by the operating system, 

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to keep track of the files that have been opened.
They're system-wide, which means the available 

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file handles are shared by every 
process running on your computer. 

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Although running out of file handles is harder 
to do these days, it's still possible with a 

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long-running process that opens a lot of files.

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Another consequence of failing to close a file, when
writing data to it, is that data might be lost. 

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Neither of these situations are good, so it's 
very important to close every file that you open. 

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Python makes this easy – it can 
close files automatically for us. 

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Back in IntelliJ, I'll 
comment out our existing code, 

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and do the same thing in a more Pythonic way:

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Line 9 uses the open function, just like before.

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But we use a with statement.
Because with is a statement, not a function, 

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we don't get a file object returned. Instead, we 
use "as jabber" to give a name to the file object. 

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Run the program:
to make sure we still get the same output. 

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Opening a file this way is preferred, 
because the file will be automatically 

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closed when the with block terminates. There's 
no chance that we'll forget to close the file, 

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and this is how I'll open 
all our files from now on. 

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This makes our code robust, and avoids 
resource leaks – such as keeping files open. 

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I'll switch to my browser, and check 
out the Resource Leak page on Wikipedia. 

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I try to explain all the terms that are used 
in this course, but if I use a term that you're 

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not familiar with, google it. Everything 
we need to know is out there, somewhere. 

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This article's quite short. A resource leak 
occurs when a program fails to release some 

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resource that it's acquired.
That could be a file handle, 

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or it could be memory (amongst other things).
We don't have to worry too much about freeing 

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up memory, because Python deals 
with memory management for us. 

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If we use with to open any resource that 
supports it, Python handles managing those 

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resources for us, as well.
I'll finish this video here. 

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Have a read through this article 
– the Causes section is interesting, 

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and starts by saying that "Resource leaks 
are generally due to programming errors". 

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Opening our files using with 
makes sure the files are closed, 

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and prevents one programming error we might make.
In the next video, we'll look at different ways 

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to read from our file, now that we know 
how to open it. See you in the next video. | www.downloadly.ir