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Notes for lecture I delivered on PythonS60 for Nokia based mobile phones to the Faculty of Technology, Makerere University

Notes for lecture I delivered on PythonS60 for Nokia based mobile phones to the Faculty of Technology, Makerere University

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  • Building mobile applications with Python over X-platforms: Part I Victor Miclovich Appfrica Labs victor.miclovich@appfrica.org September 14, 2009 Abstract converted into numbers. A screen lights up a particular coordinate (pixel) and construct an This paper exists just because it’s much more fun image with more advanced image analysis and to build something than to actually learn theoretic signal processing (we’ll cover this if we’ve got time). crap, right? What I try to put off in this article is just a way to learn Python interactively. Below is a list of data types we can expect to We shall be looking at the Python basics and encounter in Python: Graphical User Interfaces ===> [look out for other papers on Messaging, video interaction, camera • integers (int) APIs, networking, and many other topics.] • floating point (float) • strings or text (str) 1 Python basics Data types are quite easy to understand; we shall Programming languages are a way in which we can discuss ways we can handle this kind of data talk and make computers do things for us in a log- throught mathematical processes like addition, ical (or destructive) way. Like any language (both subtraction and division. natural and formal), there’s got to be a grammar of some kind, doesn’t there? The grammar in this case shall be known as a syntax . Integers integers are numbers that don’t have any Let’s think about the human language (English, fractional parts! This refers to numbers like French, ...) for a while. We see that there’s a lot 1, 2, 3, 4, ..., etc. of structure, especially, logical structure. Sentences are usually phased in particular ways that convey floats floating point are numbers with fractional the meaning a speaker intends to give the intended parts or simply decimal numbers audience. Isn’t that just so right? I think so. This Strings Strings are just textual parts of data; they is what we call having semantics. I want you could be alphabetic symbols, numbers or al- think of this as just meaning of something. phanumeric 1.1 Data types 2 Python for Symbian OS Data types defines the quality of ”things” a computer has to interface with. This is includes The Symbian OS is a mobile operating system. things like numbers and text. In essence, a Many such installations are found in many modern computer will only interact with numbers (binary Nokia, Samsung, LG phones. We shall be using i.e. {0, 1}). Images will in any case, always be Python to illustrate the design and development 1
  • of mobile applications. And while we are at it, import appuifw ready yourselves with either a phone emulator or name = appuifw.query(u"Type your the actual phone name:","text") appuifw.note(u"Hello World! Greetings We shall use Nokia smartphones as our platform from: "+str(name),"info") for learning Python in a more interesting way. Below are instructions on how to install Python in In the first line of code, we import the appuifw a Nokia (S60) phone: module, which handles user interface elements such as text input fields and popup notes. • Download the Installation files, you will find them at SourceForge’s PyS60 project page, In the second line of code, we create a single-field http://sourceforge.net/projects/pys60. Get a dialog using the query() function (think of this recent and compartable version with your as f (x, y)) which is found inside the appuifw phone. module with two parameters: label and type. The label is the text we want printed out and type – the PyS60 interpreter. (these are usually refers to whether the text should appear as a signed and have a .sis extension). warning popup, info popup, danger popup or some – the pythonscript shell (there are version other definitive standard. You may have noticed a numbers included, you should be mindful certain character u that we placed before our string of that). because the only text our phone understands is unicode: a standard way by which textual infor- • Download the Python SDK (software develop- mation is portrayed and that has internationalized ment kit); this is is at http://forum.nokia.com. support (this means many natural languages are • A phone memory/data card (you will need a supported e.g. Russian, Chinese, Arabic, etc.). place to store the programs you run for your phone). Other types are supported, not just ”text” type. They include ”number”, ”date”, ”time”, ”query”, • You will need a computer that runs either Win- and ”code”. dows, Linux or Mac OS X. • A USB cable or bluetooth to connect with the Introduction to GUIs computer. This is the easiest thing you will learn about in As we move on, you will experience the use of both PyS60 (our code name for Python in mobile). In your phone and computer; you can search for more this section I demonstrate the following stuff you tips; I will explain certain features practically. will interface with your phone in any case. • note - popup notes 3 PyS60: your first program This program consists of three lines of code; I will • query - single-field input dialog explain what each line does, but first what result do we want from the program??? • multi-query - two-field text input dialog 1. We want it to display a text input field; a place • popup menu - simple menu where the phone’s user can type in stuff! 2. Display a pop-up note that says somethig like • selection list - simple list with find pane (like ”Greetings from:” followed by whatever the a search) user typed into the input field. • multi-selection list - list to make the multiple The code is: selections 2
  • Example 1: Text input field and Dialogs, Menus, and Selection popup note lists Native UI (User Interface) elments that PyS60 of- fers are accessible through a module called: ap- Single-Field Dialog: query plication user interface framework which in code Its syntax is query(label,type[, initial is written appuifw. It is an interface to the S60 value]) UI application framework that takes care of all UI Code hack: functionalities on the S60 platform. But first an introduction to what a module is in Python. appuifw.query(u"Type a word: ", "text", u"Foo") Python lesson: module This fuction shows a single-file dialog. The dialog can include some instruction text that is passed as A module is a file that contains a collection of a string (by putting the u in front of the string ””) related functions and data grouped together. PyS60 comes with a rich set of modules, for example messaging to handle SMS functionalites, Exercise camera for taking photos, and appuifw, which The aim of this section is to allow you guys to prac- provides ready-to-use UI elements. tice! You can practice with your phone or emulator. The modules’ contents are described in detail in import appuifw the Python library reference and Python for S60 appuifw.query(u"Type a word:","text") API documentation. appuifw.query(u"Type a number:","number") To use a module (group of functionalities or abili- appuifw.query(u"Type a date:","date") ties) in your code, it must be imported at the be- appuifw.query(u"Type a time:","time") ginning of the script, for example: appuifw.query(u"Type a password:" "code") appuifw.query(u"Do you like import appuifw PyS60","query") And to pick off functionalities from your module, we write the module name, a dot and then name of function that we want! appuifw.query(label,type) Here, appuifw is the module name and query is the function you want to use. You may import many modules using a single im- port statement: import appuifw, e32 This imports two modules: appuifw and e32. In the first example several sections ago we used the query() and note() functions... (remember just like f (x)) and the functions belong to appuifw module. These functions generate UI elements, dialogs, that are displayed on the when the PyS60 interpreter executes the script. They become visible on the phone screen as soon as the corresponding Python function is called. 3