Software

A few weeks back, I posted a couple of examples of trivial (but graphical) Twitter clients. Here's a slightly more featured example, which uses the PyQt library to hook into the powerful cross-platform Qt toolkit from Python.

Here's a screenshot. It shows how many characters you have remaining, and disables posting if the character count is over the limit. Below is the code. To run on a Debian system you'd install the python-qt4 and python-httplib2 packages. I think it is a good example that for simple applications, the Python-Qt framework is pretty nice, though in lines of code, it would probably be about the same in Java (and probably less in JavaFX). Another nice thing is that you can put together the UI with Qt Designer.

Zetcode's PyQt4 tutorial and the official PyQt documentation were indispensable.

#!/usr/bin/python

import sys, urllib, httplib2
from PyQt4 import QtCore, QtGui

class PTwitter(QtGui.QWidget):

    max = 140
    uid = 'guymac'
    pwd = '********'

    twitUpdate = 'http://twitter.com/statuses/update.xml'
    twitCloser = 'http://twitter.com/account/end_session'

    def postTweet(self):
        mesg = self.txt.toPlainText()
        post = urllib.urlencode({ 'status' : mesg })

        try:
            http = httplib2.Http()

            # override the default (no exceptions, status in response)
            http.force_exception_to_status_code = False

            http.add_credentials(self.uid, self.pwd)

            resp, content = http.request(self.twitUpdate, 'POST', post)

            if resp and resp.status == 200:
                self.lbl.setText('Twitter updated!')
            else:
                raise httplib2.HttpLib2Error, 'No response'
        except httplib2.HttpLib2Error, ex:
            print ex
            self.lbl.setText(ex.__str__())

        http.request(self.twitCloser)

    def updateLabel(self):
        len = self.txt.toPlainText().size()
        self.lbl.setText('%d char(s) remaining' % (self.max-len))

        # disable the post button if chars > max
        self.pb1.setEnabled(len <= max)

    def __init__(self):
        QtGui.QWidget.__init__(self)

        # Button to post
        self.pb1 = QtGui.QPushButton('Post')

        # Button to close
        self.pb2 = QtGui.QPushButton('Close')

        # TextField for input
        self.txt = QtGui.QTextEdit()

        # Label to show characters remaining
        self.lbl = QtGui.QLabel()

        tab = QtGui.QGridLayout()
        tab.setSpacing(5)

        tab.addWidget(self.txt, 0, 0, 1, 2)
        tab.addWidget(self.lbl, 1, 0, 1, 2)
        tab.addWidget(self.pb1, 2, 0)
        tab.addWidget(self.pb2, 2, 1)

        self.setLayout(tab)
        self.setWindowTitle('PyQt4 Twitter')

        self.updateLabel()

        # connect text change to number of chars message
        self.connect(self.txt, QtCore.SIGNAL('textChanged()'),
            self.updateLabel)

        # connect post click to send message
        self.connect(self.pb1, QtCore.SIGNAL('clicked()'),
            self.postTweet)

        # connect close click to quit
        self.connect(self.pb2, QtCore.SIGNAL('clicked()'),
            QtGui.qApp, QtCore.SLOT('quit()'))

# application
app = QtGui.QApplication(sys.argv)

# window
win = PTwitter()

# display
win.show()

# execute
sys.exit(app.exec_())

I'm disappointed with O'Reilly's Python Cookbook (Second Edition). It's unfortunate because I've found their "Cookbooks" for other languages to be A) a good way to pick up the fundamentals while B) learn recipes for common programming tasks. The Python Cookbook skimps on the language fundamentals while, despite its huge bulk, having few recipes for task types that I can imagine needing to know.

For instance, there are no examples of an XPath API, which I'd consider indispensable. One of the first things I wanted to do was take the Netflix Queue XHTML and simply extract the titles. I dug up some old Java code to do it.

The chapter on XML doesn't even have any examples of creating XML! And every Python example I've seen so far does it by simply spitting out strings. Where are the equivalents of StAX, DOM, JDOM, or (wishful thinking) E4X?

I appreciate Python's attempt to be clean, consistent, and object-oriented... in marked contrast to Perl's hodge-podge gumbo of pre-OOP stuff like C, Bourne shell, and so on. But the OOP chapter is just bizarre, full of things that I've never needed to worry about in Java.

The chapters on network and web programming don't show how to post to a web server or do authentication. The online library reference is useful, but very short on complete examples. I could go on, but suffice it to say that without Google searches, I wouldn't have gotten very far with Python.