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Checking Directory Contents
6:09Once again, Python makes it easy to automate tasks. In this video let's take a look at how to search for files and directories.
One of the benefits that directories
give us is a logical grouping of files.
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We can keep all of our cat photos,
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project files or favorite rock
operas together in one place.
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Often, when we're creating software for
working with directories in files,
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we wanna be able to search for
particular files and directories.
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Luckily, Python makes this pretty easy for
us.
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So I've imported os.
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I'm gonna do os.listdir, and
you can see all of the files and
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directories that are currently
in this directory.
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Those dir method gives us back
everything that's in the directory.
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By default,
it uses the current working directory,
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but we can provide it a path
right here if you wanted to.
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And it'll tell you everything
that's in that path.
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Slightly more useful though,
is the scan dir method.
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Now we're gonna pass this one to list
because it gives us an iterable to consume
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and we wouldn't see anything good
if we didn't pass it to list.
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So we can see here all
of these dir entries.
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Each one of these dir entries is an object
that represents an entry in the directory,
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so it's either a file or
it's a directory or whatever.
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What's cool about these is we can use them
to get some basic information about their
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equivalent entry without having
to go back to the file system and
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inspect a particular file.
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For instance, let's look at this one here.
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So, 0123.
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Okay?
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So, I'm going to say
files=list(os.scandir).
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And then I'm gonna say files(3).name.
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And I get bootstrap-3.3.7-dist.zip
which you can get off
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the getbootstrap.com website.
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So let's find out if files[3] is a file.
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And it is, so cool.
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So now I can get some statistics about
the object by using the stat method.
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So I can do files[3] and
then I can say stat.
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And I get these stat results.
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Now the one of these
that is the most useful,
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the most interesting is this
one over here, this ST size.
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This is the size of the file in bytes.
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This is really handy if you wanted to,
for example,
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flag files that are above a certain size.
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Now one more thing to bring up.
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Scan dir gives you a stream like iterator.
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Like when you use the open function.
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So if you're not consuming it right away,
and then ending the block it's in.
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Like a for loop or a function.
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Or you're not using it with
a context manager like With.
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You'll want to call
the close method on it.
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So for instance if I had
scanner = os.scandir() I would
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eventually want to do scanner.close.
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That would close out the scanner and
free up memory.
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Now, let me show you another way to
work your way through directories.
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We can use the os.walk method to
step through all of the files and
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directories in a particular directory.
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This isn't exactly the same
as using scandir, but
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it gives us a handy way
to explore file trees.
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I've already started, but I'm going to
finish a script here called tree.py.
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And I say started, I've created a file.
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Now inside here, in this directory,
I have a bootstrap directory and
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that's full of all the files that
you get when you download bootstrap.
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So, I want to look through that.
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So, I'm gonna import OS, and
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then I'm gonna make a new
function named treewalker.
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And it's going to start at some directory.
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So, my total size is 0.
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And my total number of files is 0.
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So for the root, for the dirs and for
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the files that are in os.walk(start)
whatever the start directory is.
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My subtotal is going to be equal
to the sum of os.path.getsize(),
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which is similar to doing the os.stat and
then pulling out the ST_SIZE.
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But getsize just pulls directly that off.
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And I'm gonna use os.path.join,
and the root, and
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the name, and I'm gonna do that for
every name that's in files.
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And then I'm gonna say that total_size
will have the subtotal added to it.
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And I'm gonna say that file_count
will be equal to the len(files).
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Total number of files over there.
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And then total files is going
to plus equal the file count.
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Now I could of course just
combine those two lines but
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sometimes it's nice to
print the whole thing out.
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So,I'm gonna print root and then consumes.
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And I'm gonna end that with a space, and
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then I'm gonna print the subtotal,
and end that with a space.
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And then I'm gonna print bytes in,
and then the file count,
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and I'm gonna say non-directory files.
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And then out here outside of the for
loop, I'm gonna print start
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contains and then total_files.
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And then files with a combined size of,
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and then total size, and then bytes.
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So a lot of stuff to do there.
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But then I'm gonna call treewalker
down here with Bootstrap.
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There we go, save that,
come back over here, and
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I'm gonna execute tree.py.
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So Bootstrap has zero bytes,
and zero non directory files.
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Bootstrap css consumes 1.3 million
bytes in 8 non-directory files.
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Bootstrap fonts contains 215,000 bytes.
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Bootstrap.js is 117,000.
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Bootstrap in total has 16 files with
a combined size of 1.6 million bytes.
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So that's pretty cool.
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That's a really nice way just to
kind of quickly see what's going on.
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There's a lot more to the OS module, and
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we're going to explore some more
of it in the next two sections.
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Feel free though to explore
it a bit more on your own.
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It's one of the more interesting modules
in Python, especially since dealing with
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differences and operating systems
is often such a thorny area.
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All right, take a little break, have
a snack or stretch, and then come back to
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learn about manipulating files with
Python, instead of just looking at them.
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