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详细说明：“Use the Source, Luke” TheprecedingchapterintroducedPython’sclient-sideInternettoolset—thestan- dardlibrarymodulesavailableforemail,FTP,networknews,andmore,fromwithin aPythonscript.Thischapterpicksupwherethelastoneleftoffandpresentsacom- pleteclient-sideexample—PyMailGUI,aPythonprogramthatsends,recen1522420 Page 878 Friday, August 11, 2006 1: 03 PM Finally, the following are new modules coded in this chapter and are specific to the Py Mailgui program SharedNames py Program-wide globals used by multiple files ViewWindows py The implementation of View, Write, Reply, and Forward message view windows Listwindows py The implementation of mail-server and local-file message list windows PyMailGuiHelp2 py User-oriented help text, opened by the main window' s bar button The main, top-level file of the program, run to launch the main window All told, PythonMailGUI comprises the nine new modules in the preceding two lists and is composed of some 2, 200 lines of source code (including comments whitespace, and 530 lines of help text). This doesn't include the four other book examples in the previous list that are reused in PyMailGUl, which themselves consti- tute 1, 600 additional lines. This is the largest example we'll see in this book, but you shouldnt be deterred by its size. Because it uses modular and Oop techniques, the code is simpler than you may think Python's modules allow us to divide the system into files that have a cohesive purpose, with minimal coupling between them--code is easier to locate and understand if your modules have a logical, self-contained structure Pythons OOP support allows us to factor code for reuse, and avoid redun dancy--as you'll see, code is customized, not repeated, and the classes we will code reflect the actual components of the gui to make them easy to follow For instance, the implementation of mail list windows is easy to read and change because it has been factored into a common shared superclass, which is customized by subclasses for mail-server and save-file lists; since these are mostly just variations on a theme, most of the code appears in just one place. Similarly, the code that imple ments the message view window is a superclass shared by write, reply, and forward composition windows; subclasses simply tailor it for writing rather than viewing Although we'll deploy these techniques in the context of a mail processing program here, such techniques will apply to any nontrivial program you' ll write in Python And remember: you would have to multiply these line counts by a factor of four or five to get the equivalent in a language like C or C++. If you've done much programming, you probably recognize that the fact that we can implement a fairly full-featured mail processing program in roughly 2,000 lines of code speaks vol umes about the power of the Python language and its libraries. For comparison, the original version of this program from thc sccond edition of this book was just 725 lincs in 3 new modules, but also was vcry lim d-it did not sur Py Mailgul2's attach thread overlap local mail files, and 878 Chapter 15: The PyMailGUI Cli 分 n1522420 Page 879 Friday, August 11, 2006 1: 03 PM To help get you started, the PyMailGuiHelp2 py module listed last in this chapter includes a help text string that describes how this program is used, as well as its major features. Experimenting with the system, while referring to its code, is proba bly the best and quickest way to uncover its secrets Why PyMailGUI? PyMailGUI is a Python program that implements a client-side email processing user interface with the standard Tkinter gui toolkit It is presented both as an instance of Python Internet scripting and as a realistically scaled example that ties together other tools we' ve already seen such as threads and Tkinter guis Like the pymail console-based program we wrote in Chapter 14, PyMailGUI runs entirely on your local computer. Your email is fetched from and sent to remote mail servers over sockets, but the program and its user interface run locally. As a result, PyMailGUI is called an email client like pymail, it employs Pythons client-side tools Lo talk to mail servers from the local machine. Unlike pymail, though, Py MailGUI is a full-featured user interface: email operations are performed with point-and-click operations and advanced mail processing such as attachments and save files is supported Like many examples presented in this text, PyMailGUI is a practical, useful pro gram. In fact, I run it on all kinds of machines to check my email while traveling around the world teaching Python classes. Although PyMailGUI wont put Microsoft Outlook out of business anytime soon, it has two key pragmatic features that have nothing to do with email itself: portability and scriptability, which are attractive fea tures in their own right and they merit a few additional words here It's portable Py MailGUI runs on any machine with sockets and a Python with Tkinter installed. Because email is transferred with the Python libraries, any Internet connection that supports Post Office Protocol (POP) and Simple Mail Transfer Protocol (SMTP)access will do. Moreover, because the user interface is coded with Tkinter, Py Mail GUI Should work, unchanged, on Windows, the X Win dow System(Unix, Linux), and the Macintosh(classic and OS X) Microsoft Outlook may be a more feature-rich package, but it has to be run on Windows, and more specifically, on a single Windows machine. Because it gen erally deletes email from a server as it is downloaded and stores it on the client, you cannot run Outlook on multiple machines without spreading your email across all those machines. By contrast, Py MailGUI saves and deletes email onl on request, and so it is a bit friendlier to people who check their email in an ad c fashion on arbit "Use the source luke 分 n15.22420 Page 880 Friday, August 11, 2006 1: 03 PM It's scriptable Py MailguI can become anything you want it to be because it is fully program- mable. In fact, this is the real killer feature of Py MailGUI and of open source software like Python in general-because you have full access to Py MailGUI's source code, you are in complele control of where it evolves from here. You have nowhere near as much control over commercial, closed products like Outlook you generally get whatever a large company decided you need, along with what- ever bugs that company might have introduced As a Python script, Py MailGUI is a much more flexible tool. For instance, we can change its layout, disable features, and add completely new functionality quickly by changing its Python source code. Don't like the mail-list display? Change a few lines of code to customize it want to save and delete your mail automatically as it is loaded? Add some more code and buttons. Tired of seeing junk mail? Add a few lines of text processing code to the load function to filter spam. These are just a few examples. The point is that because Py MailGUI is written in a high-level, easy-to-maintain scripting language, such customizations are relatively simple, and might even be fun At the end of the day, because of such features, this is a realistic Python program that I actually use-both as a primary email tool and as a fallback option when my iSP's webmail system goes down (which, as I mentioned in the prior chapter, has a way of happening at the worst possible times). Python scripting is an enabling skill to have It's also worth mentioning that Py MailguI achieves its portability and scriptability, and implements a full-featured email interface along the way, in roughly 2, 200 lines of program code. It may not have all the bells and whistles of some commercial prod- ucts, but the fact that it gets as close as it does in so few lines of code is a testament to the power of both the python language and its libraries Running PyMailGUl Of course, to script Py mailGUI on your own, you'll need to be able to run it PyMailgui requires only a computer with some sort of internet connectivity (a pc with a broadband or dial-up account will do)and an installed Python with the Tkinter extension enabled. The Windows port of Python has this capability, so Win dows pc users should be able to run this program immediately by clicking its icon Two notes on running the system: first, you'll want to change the file mailconfig py in the program s source directory to reflect your account s parameters, if you wish to send or receive mail from a live server; more on this as we interact with the system In fact, my ISP's webmail send system went down the very day i had to submit this edition of the book to my publisher! No worrics--I fired up Py MailGUI and uscd it to send the book as attachment files through a different server. In a sense, this bock submitted itselt 880 Chapter 15: The PyMailGUI Client 分 h1522420 Page 881 Friday, August 11, 2006 1: 03 PM Second, you can still experiment with the system without a live Internet connec- tion--for a quick look at message view windows, use the main windows Open but tons to open saved-mail files stored in the programs Savedmail directory In fact, the Py Demos launcher script at the top of the books examples directory forces Py Mailgui Lo open saved-Imail files by passing filenames on the command line Presentation Strategy Py MailGUi is easily the largest program in this book, but it doesn t introduce many library interfaces that we haven t already seen in this book. For instance The PyMailGUI interface is built with Pythons Tkinter, using the familiar list- boxes, buttons, and text widgets we met earlier Pythons email package is applied to pull-out headers, text, and attachments of messages, and to compose the same ython's POP and SMTP library modules are used to fetch, send, and delete mail over sockets Python threads, if installed in your Python interpreter, are put to work to avoid blocking during potentially overlapping, long-running mail operations Were also going to reuse the TextEditor object we wrote in Chapter 12 to view and compose messages, the mailtools package's tools we wrote in Chapter 14 to load and delete mail from the server, and the mailconfig module strategy introduced Chapter 14 to support end-user settings. Py MailGUI is largely an exercise in combin- ing existing tools On the other hand, because this program is so long, we won't exhaustively docu- ment all of its code. Instead, we 'll begin by describing how py mailgUI works from an end user's perspective a brief demo of its windows in action After that, we'll list the system's new source code modules without many additional comments, for fur- ther study Like most of the longer case studies in this book this section assumes that you a ready know enough Python to make sense of the code on your own. If you've been reading this book linearly, you should also know enough about Tkinter, threads, and nail interfaces to understand the library tools applied here. If you get stuck, you may wish to brush up on the presentation of these topics earlier in the book New in this edition The 2. 1 version of Py mailGui presented in this third edition of the book is a com plete rewrite of the 1.0 version of the prior edition The main script in the second edition s version was only some 500 lines long, and was really something of a toy or prototype, written mostly to serve as a book example. In this edition, Py MailgUI is a much more realistic and full-featured program that can be used for day-to-day email "Use the source luke 881 分 n1522420 Page 882 Friday, August 11, 2006 1: 03 PM processing. It has grown to 2, 200 source lines (3, 800 including related modules that are reused). Among its new weapons are these MIME multipart mails with attachments may be both viewed and composed Mail transfers are no longer blocking, and may overlap in time Mail may be saved and processed offline from a local file Message parts may now be opened automatically within the guI Multiple messages may be selected for processing in list windows Initial downloads fetch mail headers only; full mails are fetched on request View window headers and list window columns are configurable Deletions are performed immediately, not delayed until program exit Most server transfers report their progress in the GuI Long lines are intelligently wrapped in viewed and quoted text Fonts and colors in list and view windows may be configured by the user. Authenticating SMTP mail-send servers that require login are supported. Sent messages are saved in a local file, which may be opened in the gui View windows intelligently pick a main text part to be displayed Already fetched mail headers and full mails are cached for speed Date strings and addresses in composed mails are formatted properly View windows now have quick-access buttons for attachments/parts(2. 1) Inbox out-of-sync crrors are detected on deletes, and on index and mail loads Save-mail file loads and deletes are threaded, to avoid pauses for large files(2.1) The last three items on this list were added in version 2.1; the rest were part of the 2.0 rewrite. Some of these changes were made simple by growth in standard library tools (e. g, support for attachments is straightforward with the new email package), but most represent changes in PyMailGUI itselt. There have also been a few genuine fixes addresses are parsed more accurately, and date and time formats in sent mails are now g, because these tasks use new tools in the email package Although there is still room for improvement(see the list at the end of this chapter) the program provides a full-featured interface, represents the most substantial exam le in this book and to demonstrate a realistic appl of the python lan guage. As its users often attest, Python may be fun lo work with, but it's also useful or writing pi cal and nontrivial softy 882 Chapter 15: The PyMailGUI Cli 分 n1522420 Page 883 Friday, August 11, 2006 1: 03 PM A PyMailGUI Demo Py MailGUI is a multiwindow interface. It consists of the following A main mail-server list window opened initially, for online mail processing One or more mail save-file list windows for offline mail processing One or more mail-view windows for viewing and editing messages Text editor windows for displaying the systems source code Nonblocking busy state pop-up dialogs Assorted pop-up dialogs for opened message parts, help, and more Operationally, PyMailGUI runs as a set of parallel threads, which may overlap in time: one for each active server transfer and one for each active offline save file load or deletion. Py MailGUI supports mail save files, automatic saves of sent messages configurable fonts and colors, viewing and adding attachments, main message text extraction and much more To make this case study easier to understand, let's begin by seeing what Py MailGUI actually doesits user interaction and email processing functionality-before jump into the pytho As d this free to jump ahead to the code listings that appear after the screenshots, but be sure to read this section too; this is where some subtleties of PyMailGUI's design are explained. After this section, you are invited to study the systems Python source code listings on your own for a better and more complete explanation than can be crafted in english Getting Started Py MailGUI is a Python/Tkinter program, run by executing its top-level script file Py MailGui. py. Like other Python programs, Py MailGUI can be started from the sys- tem command line by clicking on its filename icon in a tile explorer interface, or b pressing its button in the Py Demos or Py Gadgets launcher bar. However it is started the first window PyMailGUI presents is shown in Figure 15-1. Notice the"PY"win dow icon: this is the handiwork of window protocol tools we wrote earlier in this book This is the Py MailGUI main window -every operation starts here. It consists of a help button (the bar at the top A clickable email list area for fetched emails(the middle section) a button bar at the bottom for processing messages selected in the list area A PyMailGUI Demo 883 分 n15.22420 Page 884 Friday, August 11, 2006 1: 03 PM 吧Macu21 pop. car thlink nct □回 PM减 iGUl·aFyn' Tkinter enail client help U10Ew:Ew:SkiinginDubailutzrm.net Fri,27an200602:44:19 arthllnk alert: Unileve Earth￠ ustomer stpor上r,2 d Jan 200b l3:l:四 *012 Returned mail: delivery p Mail Delivery Subsystem 29 Jan 2006 5:38: 47+000 013 testing smtp I lut z(rTn.net su,29Jan200615:30:30 014 Returned mail: delivery p Mail Delivery Subsystem( 30 Jan 2006 8: 07: 51 +000 01] ELink #89: Print on Deman EarthLink Newsletter staf I Mon, 30 Jan 2006 13: 19: 08 *016ItestsendwindowupdatesIppeearthlink.net Exi,03Eeh200623:45:09 017 Re: Merica MPs file rp segearthlink net sat,04Eeh200600:23:2 o18 Re: testing sntp p3ecearthlink, net sat,04Ee200600:33:11 ng testing 12 I pp3elearthl1nknet sm,05Ee200:4:29 Load view Delete. e REply Fwd Save Open Guit Figure 15-1. Py MailG UI main server list window In normal operation, users load their email, select an email from the list area by click- ing on it, and press a button at the bottom to process it No mail messages are shown initially; we need to first load them with the Load button--a simple password input dialog is displayed, a busy dialog appears that counts down message headers being loaded to give a status indication, and the index is filled with messages ready to be selected Py MailGUI's list windows, such as the one in Figure 15-1, display mail header details in fixed-width columns, up to a maximum size Mails with attachments are prefixed with a "* in mail index list windows, and fonts and colors in Py mailgui windows may be customized by the user in the mailconfig configuration file. You can't tell in this black-and white book but by default, mail index lists are Indian red, view win- dows are a shade of purple, pop-up Py Edit windows are light cyan, and help is steel blue, you can change most of these as you like(see Example 9-11 for help with color definition strings) List windows allow multiple messages to be selected at once-the action selected at the bottom of the window is applied to all selected mails. For instance, to view many De Isplayed in its own view window. Use Ctrl-Click and Shift-Click to select more than one(the standard Windows multiple selection operations apply--try it) Before we go any further, though, let's press the help bar at the top of the list win- dow in Figure 1.5-1 to see what sort of help is available, Figure 1.5-2 shows the help window popup that appears The main part of this window is simply a block of text in a scrolled -Lext widget, along with two buttons at the bottom. The entire help text is coded as a single triple quoted string in the Python program. We could get fancier and spawn a web browser 884 Chapter 15: The PyMailGUI Client 分 n1522420 Page 885 Friday, August 11, 2006 1: 03 PM PY PYMailGUl 2. 1-Help yMailGUl, version 2.1 anuary, 2006 Programming Python, rd Fditinn ORellly Medla, Inc. PyMailGUl is a multi-window interface for processing email, both on-line and off-line Its main inte rfaces include one list window for the mail server zero or more list windows for mail save files, and multiple view windows for composIng or viewIng malls selected In a llst wIndow. On start-up, the maIn erver] list window appears first, but no mail server connection is attempted itil a Load or message send request. All PyMailGUl windows may be resized, which is especially useful in list windows to see additional columns Major enhancements in this version MIME multi-part mails with attachments may be both viewed and composed Mail transfers are nn Innger hInrking, and may nverlan in time Mail may be saved and processed off-line from a local file Message parts may now be opened automatically within the GUI Multiple messages may be selected for processing in list windows Initial downloads fetch mail headers only full mails are fetched on request view window headers and list window columns are rnnfinurahIe Deletions are performed im mediately, not delayed until program exit. SouiceCancel Figure 15-2. PyMailGUI help popup to view HTMI- formatted help, but simple text does the job here. The Cancel but- ton makes this nonmodal (i.e, nonblocking)window go away; more interestingly the Source button pops up pyEdit text editor viewer windows for all the source files of PyMailGUIs implementation; Figure 15-3 captures one of these(there are many--this is intended as a demonstration, not as a development environment). not every program shows you its source code, but PyMailGUI follows Python's open source motif When a message is selected in the mail list window, Py MailGuI downloads its full text (if it has not yet been downloaded in this session), and an email viewer window appears, as captured in Figure 15-4. View windows are built in response to actions in list windows this is described next The standard librarys webbrowser module would help for HTML-based help. Actually, the help display starred life even less fancy: it originally displayed help text in a standard information box pop up, generated by the tkinter showinfo call used earlier in the book. This worked fine on Windows(at least with a small amount of help text), but it failed on Linux bccausc of a default linc-lcngth limit in information pop-up boxes; lines were broken so badly as to be illegible A PyMailGUI Demo 88 分

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