[PyFeyn] problems with installation

[mymb1a09]

Hello

First, I'd like to thank the authors of this code which I'm keen to 
learn so that I can use it for my work.

I have ubuntu 12.04 64bit, I tried downloading the package and up to 
now, I can import it via python. But I'm facing a number of issues:

1) Even though I have PyX, I get a message saying you don't have PyX.  I 
import it along with pyfeyn but I get that message as in:

=====================
 >>> import pyx, pyfeyn
You don't have PyX - that's a problem unless you're just running the 
setup script.
=====================

2) Once I try any of the test codes provided in the website, I get a 
number of errors which I'm not sure how to interpret. For example, if I 
run the first test code I get:

===========================================
Python 2.7.3 (default, Apr 10 2013, 06:20:15)
[GCC 4.6.3] on linux2
Type "copyright", "credits" or "license()" for more information.
 >>>
You don't have PyX - that's a problem unless you're just running the 
setup script.

Traceback (most recent call last):
   File "/home/maien/Desktop/tests/pyfen/test1.py", line 27, in <module>
     fd.draw("pyfeyn-test1.pdf")
   File "build/bdist.linux-x86_64/egg/pyfeyn/diagrams.py", line 67, in draw
     c = self.drawToCanvas()
   File "build/bdist.linux-x86_64/egg/pyfeyn/diagrams.py", line 59, in 
drawToCanvas
     obj.draw(FeynDiagram.currentCanvas)
   File "build/bdist.linux-x86_64/egg/pyfeyn/lines.py", line 325, in draw
     canvas.stroke(path, styles)
   File "/usr/local/lib/python2.7/dist-packages/pyx/canvas.py", line 
298, in stroke
     self.draw(path, [deco.stroked]+list(attrs))
   File "/usr/local/lib/python2.7/dist-packages/pyx/canvas.py", line 
284, in draw
     adeco.decorate(dp, self.texrunner)
   File "build/bdist.linux-x86_64/egg/pyfeyn/deco.py", line 27, in decorate
     1, self.size, 45, constrictionlen)
TypeError: _arrowhead() takes exactly 7 arguments (6 given)
 >>>
=============================================

I'd really appreciate it if I can get help with this.

Best regards,
Maien