[Tutor] Writing to XML file with minidom

Kent Johnson kent37 at tds.net
Tue Aug 30 15:47:26 CEST 2005

Johan Geldenhuys wrote:
> That means that I have to compile the whole file from scratch in Python, 
> minidom.
> I am not that good, yet, but will try.

No, not if I understand what you are trying to do - the xmlDocument you have is all the data from the file, just write it back out using the code I posted before.

> will it be easier to search for the string that I look for in the file 
> (readlines) and then just write the pieces back again?

That depends a lot on the data. If you can reliably find what you want by looking at a line at a time, that is a simple approach. But you are almost there with the minidom. Really, just add my three lines of code to what you already have. (Maybe for prudence use a different file name.)


> Johan
> On Tue, 2005-08-30 at 07:40 -0400, Kent Johnson wrote:
>>Johan Geldenhuys wrote:
>>> Thanks for he help, so far.
>>> I am still having some questions on writing my new string back to the 
>>> xml file after I found what I was looking for and changed it.
>>> Extracts:
>>> xmlDocument = minidom.parse(file_name) # open existing file for parsing
>>> main = xmlDocument.getElementsByTagName('Config')
>>> main.getElementsByTagName('Connection')
>>> configSection = mainSection[0]
>>> for node in configSection: #Here I get the NamedNodeMap info
>>>         password = node.getAttribute("password")
>>>         # Do stuff to the password and I have 'newPass'
>>>        node.removeAttribute('password') # I take out my old attribute 
>>> and it's value
>>>        node.setAttribute('password', newPass)
>>> At this stage I have my new attribute and it's new value, but how do I 
>>> write that to my file in the same place?
>>> I have to get a 'writer', how do I do this?
>>The minidom docs say that DOM objects have a writexml() method:
>>    Write XML to the writer object. The writer should have a write() method which matches that of the file object interface.
>>This is saying that 'writer' should act like a file object. So it can just be a file object obtained by calling open(). In other words something like
>>f = open(file_name, 'w')
>>should do it. If you have non-ascii characters in your XML you should use codecs.open() instead of plain open() and encode your XML as desired (probably utf-8).
>>> Do I have to write all the data back or can I just replace the pieces I 
>>> changed?
>>You have to write it all back.
>>Tutor maillist  -  Tutor at python.org <mailto:Tutor at python.org>

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