Twisted's filepath Module

Glyph recently blogged about some of the buried treasure in Twisted, the filepath module in particular. Since working at Divmod, I've made use of this module quite a bit, and thought I'd share some of the features that I've found most useful (and intuitively nice to use).

Assuming you've got Twisted installed, let's fire up a python interpreter and import the FilePath class and instantiate it with /tmp:

>>> from twisted.python.filepath import FilePath
>>> tmp = FilePath('/tmp')

Now let's test some basic operations:

>>> tmp.exists()
True
>>> bogus = tmp.child('bogus')
>>> bogus.exists()
False

Isn't that nice? I love not having to import and use the os.path.exists function; it's a method on the object representing a file or a path, as it should be. I also enjoy the convenience FilePath offers when it comes to creating paths:

>>> mydir = tmp.child('notbogus').child('anotherdir').child('mydir')
>>> mydir.exists()
False
>>> mydir.makedirs()
>>> mydir.restat()
>>> mydir.exists()
True

We had to call restat() so that the object would check the file system again (since we just made some changes). Now, for some files:

>>> for filename in ['test1.txt', 'test2.txt', 'test3.tst']:
... mydir.child(filename).touch()
...
>>> mydir.listdir()
['test1.txt', 'test2.txt', 'test3.tst']

And if you don't believe that, we can switch to shell:

lorien:oubiwann 20:51:58 $ ls -al /tmp/notbogus/anotherdir/mydir/
total 0
drwxr-xr-x 2 oubiwann wheel 170 Feb 17 20:51 .
drwxr-xr-x 3 oubiwann wheel 102 Feb 17 20:46 ..
-rw-r--r-- 1 oubiwann wheel 0 Feb 17 20:51 test1.txt
-rw-r--r-- 1 oubiwann wheel 0 Feb 17 20:51 test2.txt
-rw-r--r-- 1 oubiwann wheel 0 Feb 17 20:51 test3.tst

Reading and writing operations are the same as usual:

>>> myfile = mydir.child(filename)
>>> myfile.isdir()
False
>>> myfile.islink()
False
>>> myfile.isfile()
True
>>> fh = myfile.open('w+')
>>> fh.write('do the usual thing')
>>> fh.close()
>>> myfile.getsize()
18L
>>> myfile.open().read()
'do the usual thing'

But you can use shortcuts like this, too:

>>> myfile.getContent()
'do the usual thing'
>>> myfile.setContent('and now for somethibg completely different...')
>>> myfile.getContent()
'and now for somethibg completely different...'

Let's get the path and recheck the file size, just to make sure:

>>> myfile.path
'/tmp/notbogus/anotherdir/mydir/test3.tst'
>>> myfile.restat()
>>> myfile.getsize()
45L

Or, again from shell:

lorien:oubiwann 20:52:06 $ ls -al /tmp/notbogus/anotherdir/mydir/
total 8
drwxr-xr-x 2 oubiwann wheel 170 Feb 17 20:58 .
drwxr-xr-x 3 oubiwann wheel 102 Feb 17 20:46 ..
-rw-r--r-- 1 oubiwann wheel 0 Feb 17 20:51 test1.txt
-rw-r--r-- 1 oubiwann wheel 0 Feb 17 20:51 test2.txt
-rw-r--r-- 1 oubiwann wheel 45 Feb 17 20:58 test3.tst

Hmm... for some reason, I really like this file and want to keep it. What do I do?

>>> docs = FilePath('/Users/oubiwann/Documents')
>>> myfile.moveTo(docs.child('special_file.txt'))

That's it! Nice, eh? Of course, we're careful, so we check to make sure it happened:

>>> myfile.exists()
False
>>> newfile = docs.child('special_file.txt')
>>> newfile.exists()
True
>>> newfile.path
'/Users/oubiwann/Documents/special_file.txt'
>>> newfile.getsize()
45L
>>> newfile.getContent()
'and now for somethibg completely different...'

To see more, check out the source, or at least do dir(FilePath) to see what other goodies this class has to offer, and enjoy :-)

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