Question

We’re using IronPython on C#, and I get different results on the console and on our application.

This code runs fine on IronPython Console:

str=[]
a = 1
b = 0
c = 1
if a==1:
   str.append('One')

if b==1:
   str.append('Two')

if c==1:
   str.append('Three')

out=','.join(str)
print out

But the same code returns an error on our application:

unexpected token 'if'

I suspect that the problem is in my newlines, because the string containing the Python code is passed through XML (XML>C#>Python):

<Set key="PythonCode" value="ipy:str=[]
a = 1
b = 0
c = 1
if a==1:
   str.append('One')

if b==1:
   str.append('Two')

if c==1:
   str.append('Three')

out=','.join(str)"/>

Other commands return expected results, my problem is with indented commands (conditions, loops).

As I don’t have access to the C# code, I look for a way to write one-liners, or any other way not to be dependent on indentation or newlines.
I tried this:

<Set key="PythonCode" value="ipy:str=[];
a = 1;
b = 0;
c = 1;
if a==1: str.append('One');
if b==1: str.append('Two');
if c==1: str.append('Three');
out=','.join(str);"/>

But I get again the same error, because there should be a blank line after each condition.

Any ideas?

Answer 1

Nonsignificant whitespace in xml is not preserved

http://www.w3.org/TR/1998/REC-xml-19980210#AVNormalize

Before the value of an attribute is passed to the application or checked for validity, the XML processor must normalize it as follows:
(…)
a whitespace character (#x20, #xD, #xA, #x9) is processed by appending #x20 to the normalized value, except that only a single #x20 is appended for a “#xD#xA” sequence that is part of an external parsed entity or the literal entity value of an internal parsed entity
(…)
If the declared value is not CDATA, then the XML processor must further process the normalized attribute value by discarding any leading and trailing space (#x20) characters, and by replacing sequences of space (#x20) characters by a single space (#x20) character.

if you want to transmit text with significant whitespace within xml tags, you need to enclose it inside a cdata section:

<<Set key="PythonCode"><![CDATA[ 

YOUR CODE HERE

]]></Set>

As far as I know, you cannot use a cdata section inside an attribute string, so you will have to change that part of your xml format to enclose the code in tags instead.

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Another workaround would be to tell your xml exporter as well as your xml importer to preserve nonsignificant whitespace.

for c# how to do this depends on which method you use to parse xml (XDocument, XmlDocument, …), see for example

http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.preservewhitespace(v=vs.71).aspx

http://msdn.microsoft.com/en-us/library/bb387014.aspx

http://msdn.microsoft.com/en-us/library/bb387103.aspx

But using cdata is definitely the better solution

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what you definitely should not do is use Whython – Python For People Who Hate Whitespace