Ivor talk about Java and Python on the first PyGrunn monthly (Jan 2012)

1. groningen.py / 16-01-2012

2. Schedule
• Input for Python meetups
• From Java to Python

3. Meetups
• groningen.py (thanks Mark)
• Talk and learn about Python development
• Community
• Regular meetings

4. What do we need?
• A time, space & some drinks
• Subjects / Format
• You!
• Please invite and suggest

5. How do you use python?
• For how long?
• Web
development?
• As main language?
• Framework?

6. Contents
• Any subject you’d like to hear about?
• Any subject you’d like to talk about?
python 3.0 web services
django 1.4 data migration
performance tuning

7. Meeting schedule
• How often?
• What day of week / time?

8. Let’s start
From Java to Python

9. Ivor Bosloper
using Geodjango
Preferred general purpose language:
Basic/
Assembler C Java Python
1985 1995 2001 2010

10. Java2py
Disclaimer: I love Java/JVM
• Typesafe/checked references
• Garbage collection
• Object Oriented
• Huge API
• General purpose
• Security, i18n
• Great debugging (e.g. with stacktraces)

11. Java2py
Why Python? Productivity!
• Readability
• Pragmatic and language possibilities
• Development cycle

12. Readability matters

13. Readability
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World");
}
}

14. Readability
@Entity
public class Farm {
@Id @GeneratedValue
private Long id;
private String name;
@ManyToOne(optional=true)
private Address address;
public Long getId() {
return this.id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return this.name;
}
DRY
public void setName(String name) {
this.name = name;
}
public Address getAddress() {
return this.address;
}
public void setAddress(Address address) {
this.address = address;
}
public String toString() {
return this.name;
}
}

15. Readability

16. Readability
No .properties, .xml, sql (/hql)

17. Readability
XML Theory:
human readable
XML Practice:
Readability of a binary
combined with the
efficiency of flat text.

18. Flexibility
• XML or .properties configuration allows only
programmed logic
• settings.py allows custom logic

19. Readability

20. Pragmatic APIs
• APIs created for use, not for possibilities
DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
Document doc = docBuilder.parse(new File("file.xml"));
XpathFactory xpf = XPathFactory.newInstance();
XPath xpath = xpf.newXPath();
NodeSet books = (NodeSet) xpath.evaluate("/Books/Book",doc,XpathConstants.NODESET);

21. Pragmatic APIs
• APIs created for use, not for possibilities
InputStream imageInputStream = FileInputStream("c.jpg");
SeekableStream seekableImageStream = SeekableStream.wrapInputStream(imageInputStream, true);
RenderedOp originalImage = JAI.create(JAI_STREAM_ACTION, seekableImageStream);
((OpImage) originalImage.getRendering()).setTileCache(null);
int origImageWidth = originalImage.getWidth();
double scale = 220.0 / originalImage.getWidth();
ParameterBlock paramBlock = new ParameterBlock();
paramBlock.addSource(originalImage); // The source image
paramBlock.add(scale); // The xScale
paramBlock.add(scale); // The yScale
paramBlock.add(0.0); // The x translation
paramBlock.add(0.0); // The y translation
RenderingHints qualityHints = new RenderingHints(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
RenderedOp resizedImage = JAI.create(JAI_SUBSAMPLE_AVERAGE_ACTION, paramBlock, qualityHints);
// lastly, write the newly-resized image to an output stream, in a specific encoding
FileOutputStream encoderOutputStream = new FileOutputStream("c-thumb.jpg");
JAI.create(JAI_ENCODE_ACTION, resizedImage, encoderOutputStream, JAI_ENCODE_FORMAT_JPEG, null);

22. Development cycle
• Getting started (Django)

23. Development cycle
Edit Save Edit Save
Reload page Reload page Compile
(2 seconds)
Restart Package
(war)
Deploy
(20 seconds)

24. Missing from py?
• Concurrency (!)
• Learn again: Performance tuning
• Safety of jvm
• (Adoption of big companies)

25. Concurrency?
• The free lunch
is over (2005)
• Azul 768-core
machine (2007)
• Python GIL in
2011?

26. Performance tuning
• Profiling
• GC options
• Memory

27. Safety of native code

28. Organizational adoption
• Commercial vendors
• Developer/deployer roles