Python_Language

Python TutorialGetting Started with PythonPython Basic SyntaxPython DatatypesPython IndentationPython Collection TypesPython Basic Input and OutputPython Built in Modules and FunctionsPython FunctionsChemPy - python packageCreating Python packagesFunctional Programming in PythonIncompatibilities moving from Python 2 to Python 3IoT Programming with Python and Raspberry PIKivy - Cross-platform Python Framework for NUI DevelopmentMutable vs Immutable (and Hashable) in PythonPyInstaller - Distributing Python CodePython *args and **kwargsPython 2to3 toolPython Abstract Base Classes (abc)Python Abstract syntax treePython Alternatives to switch statement from other languagesPython and ExcelPython Anti-PatternsPython ArcPyPython ArraysPython Asyncio ModulePython Attribute AccessPython AudioPython Binary DataPython Bitwise OperatorsPython Boolean OperatorsPython Checking Path Existence and PermissionsPython ClassesPython CLI subcommands with precise help outputPython Code blocks, execution frames, and namespacesPython Collections modulePython Comments and DocumentationPython Common PitfallsPython Commonwealth ExceptionsPython ComparisonsPython Complex mathPython concurrencyPython ConditionalsPython configparserPython Context Managers (with Statement)Python Copying dataPython CountingPython ctypesPython Data SerializationPython Data TypesPython Database AccessPython Date and TimePython Date FormattingPython DebuggingPython DecoratorsPython Defining functions with list argumentsPython DeploymentPython Deque ModulePython DescriptorPython Design PatternsPython DictionaryPython Difference between Module and PackagePython DistributionPython DjangoPython Dynamic code execution with `exec` and `eval`Python EnumPython ExceptionsPython ExponentiationPython Files & Folders I/OPython FilterPython FlaskPython Functools ModulePython Garbage CollectionPython GeneratorsPython getting start with GZipPython graph-toolPython groupby()Python hashlibPython HeapqPython Hidden FeaturesPython HTML ParsingPython HTTP ServerPython IdiomsPython ijsonPython Immutable datatypes(int, float, str, tuple and frozensets)Python Importing modulesPython Indexing and SlicingPython Input, Subset and Output External Data Files using PandasPython Introduction to RabbitMQ using AMQPStorm



Python Manipulating XML

From WikiOD

Remarks[edit | edit source]

Not all elements of the XML input will end up as elements of the parsed tree. Currently, this module skips over any XML comments, processing instructions, and document type declarations in the input. Nevertheless, trees built using this module’s API rather than parsing from XML text can have comments and processing instructions in them; they will be included when generating XML output.

Opening and reading using an ElementTree[edit | edit source]

Import the ElementTree object, open the relevant .xml file and get the root tag:

import xml.etree.ElementTree as ET
tree = ET.parse("yourXMLfile.xml")
root = tree.getroot()

There are a few ways to search through the tree. First is by iteration:

for child in root:
    print(child.tag, child.attrib)

Otherwise you can reference specific locations like a list:

print(root[0][1].text)

To search for specific tags by name, use the .find or .findall:

print(root.findall("myTag"))
print(root[0].find("myOtherTag"))

Modifying an XML File[edit | edit source]

Import Element Tree module and open xml file, get an xml element

import xml.etree.ElementTree as ET
tree = ET.parse('sample.xml')
root=tree.getroot()
element = root[0] #get first child of root element

Element object can be manipulated by changing its fields, adding and modifying attributes, adding and removing children

element.set('attribute_name', 'attribute_value') #set the attribute to xml element
element.text="string_text"

If you want to remove an element use Element.remove() method

root.remove(element)

ElementTree.write() method used to output xml object to xml files.

tree.write('output.xml')

Create and Build XML Documents[edit | edit source]

Import Element Tree module

import xml.etree.ElementTree as ET

Element() function is used to create XML elements

p=ET.Element('parent')

SubElement() function used to create sub-elements to a give element

c = ET.SubElement(p, 'child1')

dump() function is used to dump xml elements.

ET.dump(p)
# Output will be like this
#<parent><child1 /></parent>

If you want to save to a file create a xml tree with ElementTree() function and to save to a file use write() method

tree = ET.ElementTree(p)
tree.write("output.xml")

Comment() function is used to insert comments in xml file.

comment = ET.Comment('user comment')
p.append(comment) #this comment will be appended to parent element

Opening and reading large XML files using iterparse (incremental parsing)[edit | edit source]

Sometimes we don't want to load the entire XML file in order to get the information we need. In these instances, being able to incrementally load the relevant sections and then delete them when we are finished is useful. With the iterparse function you can edit the element tree that is stored while parsing the XML.

Import the ElementTree object:

import xml.etree.ElementTree as ET

Open the .xml file and iterate over all the elements:

for event, elem in ET.iterparse("yourXMLfile.xml"):
    ... do something ...

Alternatively, we can only look for specific events, such as start/end tags or namespaces. If this option is omitted (as above), only "end" events are returned:

events=("start", "end", "start-ns", "end-ns")
for event, elem in ET.iterparse("yourXMLfile.xml", events=events):
    ... do something ...

Here is the complete example showing how to clear elements from the in-memory tree when we are finished with them:

for event, elem in ET.iterparse("yourXMLfile.xml", events=("start","end")):        
    if elem.tag == "record_tag" and event == "end":
        print elem.text
        elem.clear()
    ... do something else ...

Searching the XML with XPath[edit | edit source]

Starting with version 2.7 ElementTree has a better support for XPath queries. XPath is a syntax to enable you to navigate through an xml like SQL is used to search through a database. Both find and findall functions support XPath. The xml below will be used for this example

 <Catalog>
    <Books>
        <Book id="1" price="7.95">
            <Title>Do Androids Dream of Electric Sheep?</Title>
            <Author>Philip K. Dick</Author>
        </Book>
        <Book id="5" price="5.95">
            <Title>The Colour of Magic</Title>
            <Author>Terry Pratchett</Author>
        </Book>
        <Book id="7" price="6.95">
            <Title>The Eye of The World</Title>
            <Author>Robert Jordan</Author>
        </Book>
    </Books>
</Catalog>

Searching for all books:

import xml.etree.cElementTree as ET
tree = ET.parse('sample.xml')
tree.findall('Books/Book')

Searching for the book with title = 'The Colour of Magic':

tree.find("Books/Book[Title='The Colour of Magic']") 
# always use '' in the right side of the comparison

Searching for the book with id = 5:

tree.find("Books/Book[@id='5']")
# searches with xml attributes must have '@' before the name

Search for the second book:

tree.find("Books/Book[2]")
# indexes starts at 1, not 0

Search for the last book:

tree.find("Books/Book[last()]")
# 'last' is the only xpath function allowed in ElementTree

Search for all authors:

tree.findall(".//Author")
#searches with // must use a relative path

Credit:Stack_Overflow_Documentation