How to update existing xml element with new given element using python?

Question

I have input XML as country.xml:-

<root>
<set>
    <name>Countries</name>
    <elements>
    <name>US</name>
    <city>
        <val>New York</val>
        <val>Las Vegas</val>
    </city>
    </elements>
    <elements>
    <name>UK</name>
    <city>
        <val>London</val>
    </city>
    </elements>
</set>
</root>

I am parsing xml and taking it into a list and i have a dictionary based on which I am comparing and adding xml elements.

diction: dict = {'US':['New York', 'Chicago'], 'UK':['OXFORD', 'London']}
source = etree.getroot()
for key,value in diction.items()
    countrylist = source.xpath('./elements/name[text()=\'{}\']/..'.format(key))
    if len(countrylist) == 0:
        # creating new string and element
        # appending element to original tree
    elif len(countrylist) == 1:   ###This is problematic case what to expect here to update key,value from dictionary only and replace the tag already present in xml
        key = countrylist[0]
    else:
        countinue

    # writebacktoxml(source,"country.xml")

Output I am getting is original input condition as it is in output for specific condition. Expected output is below:-

<root>
<set>
    <name>Countries</name>
    <elements>
    <name>US</name>
    <city>
        <val>New York</val>
        <val>Chicago</val>
    </city>
    </elements>
    <elements>
    <name>UK</name>
    <city>
        <val>OXFORD</val>
        <val>London</val>
    </city>
    </elements>
</set>
</root>

key = countrylist[0] does not update your xml. It only creates a new reference/variable key pointing to countrylist[0] — nauer
– nauer, Commented Jan 9, 2019 at 13:53
@stovfl- how to go about it...can you please suggest it will be of great help — Pyjava
– Pyjava, Commented Jan 9, 2019 at 15:50

stovfl · Accepted Answer · 2019-01-09 17:04:38Z

1

Comment: What if diction:{'AUSTRALIA': ['MELBOURNE']} ? And I want to keep both the things from dictionary as well as from input xml into output xml?

Add a condition around .clear

if name.text in ['AUSTRALIA']:
    # Keep the values
    pass
else:
    table_category.clear()

Question: How to update existing xml element with new given <val>...</val>?

Documentation: The lxml.etree Tutorial - The E-factory
Python Documentation -The ElementTree XML API - Modifying an XML File

Example using lxml

from lxml import etree
from lxml.builder import ElementMaker

Data dict

diction = {'US': ['New York', 'Chicago'], 'UK': ['OXFORD', 'London']}

Instantiate a ElementMaker object and a new <val>...</val> object.
```
E = ElementMaker()
VAL = E.val
```

Parse the source xml

tree = etree.parse(io.StringIO(xmlf))
root = tree.getroot()

Parse all set/elements

for element in root.findall('set/elements'):

Get the name of this element
```
    name = element.find('name')
```

Get the table_category of this element and .clear it

    table_category = element.find('table_category')
    table_category.clear()

Loop all items from the list in diction defined for [name.text].
```
    for val in diction[name.text]:
```

Append a new <val>val</val> to table_category

        table_category.append(VAL(val))

Output: print('{}'.format(etree.tostring(root, pretty_print=True).decode()))

<configroot version="8.0">
<set>
    <name>Countries</name>
    <elements>
    <name>US</name>
    <table_category><val>New York</val><val>Chicago</val></table_category></elements>
    <elements>
    <name>UK</name>
    <table_category><val>OXFORD</val><val>London</val></table_category></elements>
</set>
</configroot>

Tested with Python: 3.5

edited Jan 9, 2019 at 17:04

answered Jan 9, 2019 at 16:21

stovfl

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4 Comments

Pyjava Over a year ago

Thanks it's working now any other alternative for builder or is it inbuilt under lxml?

stovfl Over a year ago

@Pyjava: " any other alternative for builder or is it inbuilt under lxml": Can't answer this for sure, added the Documentation link to my answer.

Pyjava Over a year ago

What if diction:{'AUSTRALIA': ['MELBOURNE']} ? And I want to keep both the things from dictionary as well as from input xml into output xml? There is a test case failure in that case.

Pyjava Over a year ago

Similar thing in stackoverflow.com/questions/54124953/… .......just that it does not has table_category then how would i update the stringval?

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