Download User Interface Software & Technology

Jython & Swing
Building a UI in a high-level
language
Agenda
Overview of Jython
Using Swing in Jython
Jython and Eclipse
HW 1
Python
A very high-level language
“Pseudo-code that runs”
Tutorial and documentation at:
http://www.python.org
Jython
Implementation of Python in Java
http://www.jython.org
Ease of Python, plus access to Java
class libraries
Overview of Jython
Interpreted
 Dynamic (run-time) strong typing

– No need to declare variables
Modules, classes, functions
 Built-in types: tuples, lists,
dictionaries

Jython Syntax
Whitespace is used to delimit blocks
for i in range(5):
if i < 2:
print i
print “Done”
Jython Conditional Logic
if expression:
block
elif expression:
block
else:
block
Jython boolean logic
Generally….
Non-zero is true, 0 is false
Objects are true, None* is false
Empty lists are false
use: and, or, not
* None is the equivalent of Null
Jython Loops
while expression:
block
else:
block
# exits once on normal
# loop end
Note: pass, break, continue
Jython Loops
For variable in sequence:
block
else:
block
Jython Loops
for x in (‘a’, 5, [1, 2]):
print x
for x in range(10):
print x
# prints 0, 1, 2, …, 9
for key, value in dict.items():
print key, “ : ” , value
Jython List Comprehensions
[expression for value in sequence]
newList = [x + 2 for x in (1, 2, 3)]
Jython Lists
Heterogeneous, mutable
l = [1, ‘test’, [9, 10], 5]
len(l)
#4
l[1] = ‘foo’
# [1, ‘foo’, [9, 10], 5]
l.remove(5)
# [1, ‘foo’, [9, 10]]
l.append(2)
# [1, ‘foo’, [9, 10], 2]
newList = l[2:4] # [[9, 10], 2]
Jython Strings
s1 = ‘This is a string.’
s2 = “So is this.”
s3 = s1 + ‘ ‘ + s2
s2.split()
# [‘So’, ‘is’, ‘this.’]
s2.find(‘is’)
#3
Jython Tuples
Heterogeneous, immutable
t = (‘example’, 1, [1, 2])
len(t)
#3
t[1]
#1
t[1] = 3
# TypeError
Jython Dictionaries
(Key, value) pairs, similar to hash tables
dict = {‘one’: 1, 2 : ‘two’ }
dict.keys()
# [‘one’, 2]
dict.values()
# [1, ‘two’]
dict[3] = 4
dict.items()
# [(‘one’, 1),
# (2, ‘two’), (3, 4)]
del dict[3]
Jython Exception Handling
try:
block
except: / except exception-type:
block
else:
block # if no exceptions raised
Jython Exception Handling
try:
block
finally:
block
# executed even if exception
Jython lambda functions
f = lambda x, y: x + y + 2
f(1, 2)
#5
Jython Functions
def FuncName(args):
block
def AddNumbers(a , b):
return a + b
Jython Functions
Keyword arguments and default values
def AddSome(a, b=9, c=10):
return a + b + c
AddSome(1, 2, 3)
AddSome(1, 2)
AddSome(1)
#6
# 13
# 20
Jython Classes
class MyClass:
def __init__(self, aValue = 5):
self.aField = aValue
def addToField(self, aNumber)
self.aField += aNumber
def printField(self):
print self.aField
inst1 = MyClass()
inst2 = MyClass(10)
inst1.aField = 6
inst1.addToField(1)
inst1.printField()
MyClass.printField(inst2)
#7
# 10
Jython Classes: Inheriting
class MyNewClass(MyClass):
def __init__(self):
MyClass.__init__(self, 8)
inst = MyNewClass()
inst.aField
#8
Jython: Prototype-Instance
inst = MyClass()
inst.b = ‘test’
inst.b
# test
Jython Modules
Basic unit for managing namespace
Usually a file full of code (.class, .jar, .py)
import javax.swing
import javax.swing as swing
from javax.swing import JFrame
from javax.swing import *
Swing
Essentially a library of classes for
building GUIs
Part of the Java Foundation Classes
Online tutorial:
http://java.sun.com/docs/books/tutorial/uiswing/
Useful Swing Classes
JFrame (essentially a window)
JLabel
JButton
JTextField
JTextArea
JMenuBar
JScrollPane
JPanel
JPasswordField
JTable
Jython and Swing
Can work with Java classes from within Jython
import javax.swing as swing
frame = swing.JFrame(‘Hello World Swing’)
frame.setDefaultCloseOperation(
swing.JFrame.EXIT_ON_CLOSE)
label = swing.JLabel(“Hello World”)
frame.getContentPane().add(label)
frame.pack()
frame.setVisible(1)
Jython and JavaBean Properties
Replace object.getFoo() and
object.setFoo(newFoo) with:
object.foo
object.foo = newFoo
Can also assign in constructor
object = MyClass(foo = newFoo)
Jython and JavaBean Properties
Code becomes:
import javax.swing as swing
frame = swing.JFrame(‘Hello World Swing’,
defaultCloseOperation = swing.JFrame.EXIT_ON_CLOSE)
label = swing.JLabel(“Hello World”)
frame.contentPane.add(label)
frame.pack()
frame.visible = 1
Jython, Swing, and Listeners
Jython also handles Listener wrapping for you
Instead of:
int count = 1;
JButton button = new JButton(“Increment”);
button.addActionListener(
new ActionListener{
public void actionPerformed(ActionEvent e) {
count++;
})
Use:
count = 1
def Increment(event):
count += 1
button = swing.JButton(“Increment”, actionPerformed = Increment)
Quick Jython & Java notes
Jython classes can subclass Java classes (and
interfaces)
You can embed Jython in Java
You can compile Jython to Java
Type conversion can be a little subtle
http://www.jython.org/docs/usejava.html
Learning More
Python and Jython websites
 Jython for Java Programmers

– $34 on Amazon

Jython Essentials
– $17 on Amazon
HW 1
Create a simple email client
- Uses POP or IMAP to read Inbox
- Uses SMTP to send email
- UI to check mail, display Inbox
- UI to read message
- UI to send new mail, reply, forward
Due Sept. 9 (next Thursday)
Useful Jython libraries
poplib – implements POP3
smtplib – implements SMTP
imaplib – implements IMAP4
rfc822 – parsing email message (possibly)
poplib
import poplib
M = poplib.POP3(‘gvu1.cc.gatech.edu')
M.user( ‘jpierce’)
M.pass_(‘mypassword’)
numMessages = len(M.list()[1])
for i in range(numMessages):
for j in M.retr(i+1)[1]:
print j
smtplib
import smtplib
server = smtplib.SMTP(‘gvu1.cc.gatech.edu’)
server.sendmail(fromaddr, toaddrs, msg)
server.quit()
Eclipse and Jython
Eclipse
- http://www.eclipse.org/
Jython
- Red Robin Jython plug-in
- http://home.tiscali.be/redrobin/jython/
Next Time
Interaction Models
Formal
Informal