Remove the file xml.py or a directory xml with a file __init__.py in it from your current directory and try again. Python will search the current directory first when importing modules. A file named xml.py or a package named xml in the current directory shadows the standard library package with the same name.

As pointed out in a comment by KeshV, you also need to remove the file xml.pyc, if it exists. In Python 2 it will be in the same directory as xml.py. In Python 3 it will be in the sub directory __pycache__. In General, as long as the *.py file is around, you can savely delete the corresponding *.pyc file because Python will re-create it upon import of the *.py file.

Use the xmldiff to perform this exact task.

main.py

from xmldiff import main
diff = main.diff_files("file1.xml", "file2.xml")
print(diff)

output

[DeleteNode(node='/ngs_sample/results/gastro_prelim_st/type[2]')]

Edit: Have you named your script: xml.py? Change it and it should work.

As a workaround, you could use etree in the lxml package. If you don't have lxml installed, type:

sudo apt-get install python-lxml

And for the modified version of your program:

import lxml.etree as ET 

root = ET.Element("root") 
doc = ET.SubElement(root, "doc") 
field1 = ET.SubElement(doc, "field1") 
field1.set("name", "blah") 
field1.text = "some value1" 
field2 = ET.SubElement(doc, "field2") 
field2.set("name", "asdfasd") 
field2.text = "some vlaue2" 
tree = ET.ElementTree(root) 
tree.write("filename.xml") 

Output:

<root>
   <doc>
        <field1 name="blah">some value1</field1>
        <field2 name="asdfasd">some vlaue2</field2>
   </doc>
</root>

For differences between the two solutions, lxml.etree and ElementTree, have a look at this doc lxml.etree versus ElementTree.

cElementTree is slightly faster compared to lxml.etree, anyway the latter is still a fast xml parser written in C, and I think the difference is negligible (benchmarks here).