Re: [Tutor] Writing to XML file with minidom
On 8/31/05, Danny Yoo <[EMAIL PROTECTED]> wrote: > Hi Travis, Hey Danny, > Putting pure binary bytes in an XML file has a flaw: the issue is that the > binary bytes themselves might contain characters that could be interpreted > as XML! Even if we wrap the content in CDATA, there's nothing that really > stops the bytes from containing the characters "]]>" to prematurely close > off the CDATA tag. Oh, sure. I didn't think that through, and if I had, I wouldn't have know how to work around it. > To get around this, we can use a technique called "ascii-armor" to wrap > protection around the troublesome binary text. > > http://en.wikipedia.org/wiki/ASCII_armor Brilliant. I won't forget the term "ascii-armor" if I ever find myself in Johan's shoes and I've forgotten the details. > (Hey, look, an Elf! *grin*) HA! > Hope this helps! Tremendously. Thanks, Danny! -- Regards, Travis Spencer ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Writing to XML file with minidom
> > One snag that I found is that the des encryption that I used for the
> > data that is written back, it is not parsed correctly when the file is
> > read again with the new data in it. There is non-printable characters
> > or non-ascii chars in that gives errors from expat when the contents
> > is parsed. I had to use a different encryption algorithm. I am going
> > to do some tests on it now.
>
> Put the cyphertext in a CDATA section, so the parser knows to ignore
> its contents:
>
>
>
>
>
>
Hi Travis,
Putting pure binary bytes in an XML file has a flaw: the issue is that the
binary bytes themselves might contain characters that could be interpreted
as XML! Even if we wrap the content in CDATA, there's nothing that really
stops the bytes from containing the characters "]]>" to prematurely close
off the CDATA tag.
To get around this, we can use a technique called "ascii-armor" to wrap
protection around the troublesome binary text.
http://en.wikipedia.org/wiki/ASCII_armor
Python comes with a common ascii-armoring algorithm called "base64", and
it's actually very easy to use it. Let's do a quick example.
Let's say we have some binary unprintable bytes, like this:
##
>>> someBytes = open('/usr/bin/ls').read(8)
>>> someBytes
'\x7fELF\x01\x01\x01\x00'
##
(Hey, look, an Elf! *grin*)
Anyway, this ELF will probably pass through email poorly, because the
bytes surrounding it are pretty weird. But we can apply base64 encoding
on those bytes:
##
>>> encodedBytes = someBytes.encode('base64')
>>> encodedBytes
'f0VMRgEBAQA=\n'
##
And now it's in a form that should pass cleanly through. Decoding it is
also a fairly easy task:
##
>>> encodedBytes.decode('base64')
'\x7fELF\x01\x01\x01\x00'
##
And now we've got our ELF back.
Hope this helps!
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Re: [Tutor] Writing to XML file with minidom
On 8/30/05, Johan Geldenhuys <[EMAIL PROTECTED]> wrote: > One snag that I found is that the des encryption that I used for the data > that is > written back, it is not parsed correctly when the file is read again with the > new > data in it. There is non-printable characters or non-ascii chars in that > gives errors > from expat when the contents is parsed. > I had to use a different encryption algorithm. I am going to do some tests on > it > now. Put the cyphertext in a CDATA section, so the parser knows to ignore its contents: -- Regards, Travis Spencer P.S. Please don't send HTML e-mails. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Writing to XML file with minidom
Kent,
Thanks for the tip. I can write the changed data back to my xml file. One snag that I found is that the des encryption that I used for the data that is written back, it is not parsed correctly when the file is read again with the new data in it. There is non-printable characters or non-ascii chars in that gives errors from expat when the contents is parsed.
I had to use a different encryption algorithm. I am going to do some tests on it now.
Johan
On Tue, 2005-08-30 at 09:47 -0400, Kent Johnson wrote:
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.)
Kent
>
> 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:
>>writexml(writer[,indent=""[,addindent=""[,newl=""]]])
>>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')
>>xmlDocument.writexml(f)
>>f.close()
>>
>>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.
>>
>>Kent
>>
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>
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Re: [Tutor] Writing to XML file with minidom
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.)
Kent
>
> 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:
>>writexml(writer[,indent=""[,addindent=""[,newl=""]]])
>>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')
>>xmlDocument.writexml(f)
>>f.close()
>>
>>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.
>>
>>Kent
>>
>>___
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>>http://mail.python.org/mailman/listinfo/tutor
>>
>
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Re: [Tutor] Writing to XML file with minidom
That means that I have to compile the whole file from scratch in Python, minidom.
I am not that good, yet, but will try.
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?
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:
writexml(writer[,indent=""[,addindent=""[,newl=""]]])
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')
xmlDocument.writexml(f)
f.close()
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.
Kent
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Re: [Tutor] Writing to XML file with minidom
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:
writexml(writer[,indent=""[,addindent=""[,newl=""]]])
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')
xmlDocument.writexml(f)
f.close()
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.
Kent
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Re: [Tutor] Writing to XML file with minidom
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?
Do I have to write all the data back or can I just replace the pieces I changed?
Thanks,
Johan
--- Begin Message ---
> """ Parse the xml file """
> xmlDocument = minidom.parse(self.configFile)
[code cut]
> Now I want to change a string that a retrieved from the file and write
> it back to where it was. So, I get something, change it and write it
> back.
>
> How do I put the new string in the place of the old? How do I overwrite
> the first value with the new value?
Hi Johan,
The documentation in:
http://www.python.org/doc/lib/module-xml.dom.minidom.html
has a small example where they insert text into an element:
## (From the documentation)
from xml.dom.minidom import getDOMImplementation
impl = getDOMImplementation()
newdoc = impl.createDocument(None, "some_tag", None)
top_element = newdoc.documentElement
text = newdoc.createTextNode('Some textual content.')
top_element.appendChild(text)
##
Elements have methods like appendChild(), replaceChild() and
removeChild(). So it should be fairly straightforward to replace the
existing text node with a new one.
That being said, the DOM model is a bit verbose and feels very low-level.
Have you looked at the third-party "ElementTree" module yet?
http://effbot.org/zone/element-index.htm
It's a bit more convenient to work with; its model maps better to Python.
Good luck!
--
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Enjoy Your Day.
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Re: [Tutor] Writing to XML file with minidom
> """ Parse the xml file """
> xmlDocument = minidom.parse(self.configFile)
[code cut]
> Now I want to change a string that a retrieved from the file and write
> it back to where it was. So, I get something, change it and write it
> back.
>
> How do I put the new string in the place of the old? How do I overwrite
> the first value with the new value?
Hi Johan,
The documentation in:
http://www.python.org/doc/lib/module-xml.dom.minidom.html
has a small example where they insert text into an element:
## (From the documentation)
from xml.dom.minidom import getDOMImplementation
impl = getDOMImplementation()
newdoc = impl.createDocument(None, "some_tag", None)
top_element = newdoc.documentElement
text = newdoc.createTextNode('Some textual content.')
top_element.appendChild(text)
##
Elements have methods like appendChild(), replaceChild() and
removeChild(). So it should be fairly straightforward to replace the
existing text node with a new one.
That being said, the DOM model is a bit verbose and feels very low-level.
Have you looked at the third-party "ElementTree" module yet?
http://effbot.org/zone/element-index.htm
It's a bit more convenient to work with; its model maps better to Python.
Good luck!
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[Tutor] Writing to XML file with minidom
Hi all,
I use minidom to parse xml data from a file.
I know how to get the data:
"""
""" Parse the xml file """
xmlDocument = minidom.parse(self.configFile)
""" Parse xml main section """
mainSection = xmlDocument.getElementsByTagName('Config')
""" Parse xml Global section """
configSection = mainSection[0]
""" Parse Ports section """
socketList = configSection.getElementsByTagName('Sockets')
"""
Now I want to change a string that a retrieved from the file and write it back to where it was. So, I get something, change it and write it back.
How do I put the new string in the place of the old? How do I overwrite the first value with the new value?
Thanks,
Johan
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