how to write xml back to a file-CodePudding

I have about 100,000 price-table records in XML and I need to remove entries where the price amount is 0.00. The data is structured as follows:

<data>
    <price-table product-id="100109a">
        <amount quantity="1">10.00</amount>
    </price-table>
    <price-table product-id="201208c">
        <amount quantity="1">0.00</amount>
    </price-table>
</data>

I'm trying to use Python to do the work and I have the following:

from xml.etree import ElementTree as ET

def readfile():
    with open('prices.xml') as f:
        contents = f.read()
        return(contents)

xml_string = readfile()

root = ET.fromstring(xml_string)

for price_table in root.findall('price-table'):
    amount = price_table.find('amount')
    if float(amount.text) != 0:
        root.remove(price_table)

xmltowrite = ET.tostring(root)
#print(xmltowrite)

with open('xmlwrite.txt', 'w') as j:
    j.write(xmltowrite)

When I run this, the error I get is:

TypeError: write() argument must be str, not bytes

But my understanding is that the ET.tostring() function should be converting the xmltowrite value to a string... Why is that not a string at the end?

CodePudding user response：

If you print the type(xmltowrite) you will see it's a <class 'bytes'>. You can decode it with ET.tostring(root).decode("Utf-8"), than you get <class 'str'>.

CodePudding user response：

tostring() returns a bytes object unless encoding="unicode" is used.

The code can be simplified quite a bit. There is no need to use open(), fromstring() or tostring(). Just parse the XML file into an ElementTree object, do your changes, and save using ElementTree.write().

from xml.etree import ElementTree as ET

tree = ET.parse("prices.xml")
root = tree.getroot()

for price_table in root.findall('price-table'):
    amount = price_table.find('amount')
    if float(amount.text) != 0:
        root.remove(price_table)

tree.write('xmlwrite.txt')