Example: Extracting data from an existing ISO
This example will show how to extract data from an existing ISO. Here’s the complete code for this example:
try:
from cStringIO import StringIO as BytesIO
except ImportError:
from io import BytesIO
import pycdlib
iso = pycdlib.PyCdlib()
iso.new()
foostr = b'foo\n'
iso.add_fp(BytesIO(foostr), len(foostr), '/FOO.;1')
out = BytesIO()
iso.write_fp(out)
iso.close()
iso.open_fp(out)
extracted = BytesIO()
iso.get_file_from_iso_fp(extracted, iso_path='/FOO.;1')
iso.close()
print(extracted.getvalue().decode('utf-8'))
Let’s take a closer look at the code.
try:
from cStringIO import StringIO as BytesIO
except ImportError:
from io import BytesIO
import pycdlib
As we’ve seen before, import pycdlib. We also import the BytesIO module so we can use a python string as a file-like object.
iso = pycdlib.PyCdlib()
iso.new()
foostr = b'foo\n'
iso.add_fp(BytesIO(foostr), len(foostr), '/FOO.;1')
out = BytesIO()
iso.write_fp(out)
iso.close()
This code creates a new ISO, adds a single file to it, and writes it out. This is very similar to the code in Creating a new, basic ISO, so see that example for more information. One important difference in this code is that it uses a BytesIO object to master the ISO into so we don’t have to write any temporary data out to the filesystem; it all happens in memory.
iso.open_fp(out)
Here we open up the ISO we created above. We can safely re-use the PyCdlib object because we called the close method earlier. Also note that we use open_fp to open the file-like object we wrote into using write_fp above.
extracted = BytesIO()
iso.get_file_from_iso_fp(extracted, iso_path='/FOO.;1')
Now we use the get_file_from_iso_fp API to extract the data from a file on the ISO. In this case, we access the “/FOO.;1” file that we created above, and write out the data to the BytesIO object extracted.
iso.close()
print(extracted)
As is the case in other examples, we close out the PyCdlib object, and print out the data we extracted.