source: branches/uq/lang/python/README @ 5410

Last change on this file since 5410 was 5410, checked in by mmh, 9 years ago

add new python API, PyXml?

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1------------------------------------------------------------------------
2 Rappture - Rapid APPlication infrastrucTURE
3------------------------------------------------------------------------
4 The Rappture toolkit provides the basic building blocks for many
5 scientific applications.  These blocks can be composed using C++, or
6 a high-level language, such as Python.  Having a set of blocks for
7 basic I/O, meshing, and numerical methods, a scientist can then
8 focus on developing his core algorithm.
9------------------------------------------------------------------------
10 AUTHORS:
11   Michael J. McLennan, Purdue University
12   Copyright (c) 2004-2012  HUBzero Foundation, LLC
13
14 See the file "license.terms" for information on usage and
15 redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
16------------------------------------------------------------------------
17
18
19 INSTALLATION
20------------------------------------------------------------------------
21 This part of the Rappture toolkit works with Python.  If you need to
22 install Python on your system, visit the Download section of the site
23 http://www.python.org.
24
25 Assuming you already have Python installed, you can install Rappture
26 as follows:
27
28   % cd rappture/python
29   % python setup.py install
30
31 This will make Rappture a part of your normal Python installation, so
32 you can use it in your own Python scripts, as shown below.
33
34
35 GETTING STARTED
36------------------------------------------------------------------------
37 Here is a quick tutorial to get you started using Rappture in your
38 Python scripts.
39
40 Rappture applications load their data from a an XML driver file.
41 In the tool.xml file, you should have something like
42
43 <command> @tool/path/to/executable @driver </command>
44
45The "@driver" pattern is replaced by the driver xml file generated by
46Rappture.  This driver file will contain the values to use for the
47parameters in your application.  See
48https://nanohub.org/infrastructure/rappture/wiki/rappture_xml_elements
49for more information.
50
51The first thing your application should do is load the driver file.
52
53   import Rappture
54   rx = Rappture.PyXml('example.xml')
55
56You can see the xml contents by doing
57   print rx.xml()
58
59 The "import" statement loads the Rappture toolkit into your Python
60 application.  The next line creates a library object representing
61 the data in the "example.xml" file.  The last line prints the
62 contents of the XML library to the screen.
63
64 You can access values within the XML by using the get() method.
65 For example,
66
67   import Rappture
68   lib = Rappture.PyXml('example.xml')
69   tval = lib.get('group(ambient).number(temp).current')
70or alternatively
71   tval = lib['group(ambient).number(temp).current'].value
72
73 The get() method follows a path through the XML.  In this example,
74 it looks for a <group id="ambient"> tag, and then finds the
75 <number id="temp"> tag within it, then finds the <current> tag
76 within it, and then returns the text between that and the closing
77 </current> tag.
78
79 You can also add new data to the XML by using the put() method.
80 For example, we could change the temperature value that we queried
81 above as follows:
82
83   tval += 10
84   lib.put('group(ambient).number(temp).current', tval)
85or
86   lib[group(ambient).number(temp).current'] = tval
87
88 This changes the text within the <current>...</current> tag,
89 replacing it with the new value, converted to a string if necessary.
90
91 You can also append to an existing value.  For example,
92
93   lib.put('group(ambient).number(temp).current', 'more text', append=1)
94
95 This adds the string 'more text' after the value (tval) within the
96 <current>...</current> tag.  Use of append in a loop is not
97 recommended because it can be very slow.  It is faster to collect
98 data in python and put it all at once.
99
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