Wiley Professional IronPython
Contents
1. X Frames Enables basic sys _getframe support X FullFrames Enables sys _getframe with access to local objects and variables x GcStress Specifies the garbage collector GC stress level Stressing the GC can point out potential resource problems in your application X LightweightScopes Generates optimized scopes that are easier for the GC to collect Optimizing GC functionality tends to improve the overall performance both speed and reliability of your application X MaxRecursion Determines the maximum recursion level within the application Recursion can use a lot of system resources so controlling the amount of recursion tends to reduce resource usage by applications that rely on recursion Of course reducing the recursion levels can also cause application exceptions X MTA Runs the application in a multithreaded apartment MTA X NoAdaptiveCompilation Disables the adaptive compilation feature X PassExceptions Tells the interpreter not to catch exceptions that are unhandled by script code X PrivateBinding Enables binding to private members X Python30 Enables available Python 3 0 features such as classic division where dividing two integers produces an integer result X ShowClrExceptions Displays the Common Language Specification CLS exception information X TabCompletion Enables TabCompletion mode X Tracing Enables support for tracing all methods even before the code calls sys settr2. ll find that IronPython does a lot of work for you in the background dynamically as explained earlier in the chapter Save the code you ve typed into Notepad as MyFirst py Make sure you choose All Files in the Save As Type field so that Notepad doesn t add a txt extension to the output To execute this example type IPY MyFirst py at the command line and press Enter Figure 1 10 shows the output from this quick example 22 CHAPTER1 DISCOVERING IRONPYTHON c C WINDOWS system32 cmd exe 255 Source Code Chapter 1 gt IPY MyFirst py 10 5 255 Source Code Chapter 1 gt FIGURE 1 10 The output of the example is a simple equation USING IRONPYTHON CONSTRUCTIVELY This chapter has introduced you to IronPython You should have a good understanding of why you want to use IronPython and how it differs from other static NET languages Dynamic languages have a special place in your toolbox They aren t the answer to every need but they can address specific needs just as other languages address the needs for which they were built At the end of the day the computer doesn t care what language you use the computer simply cares how that language is translated into the bits and bytes it requires to do something useful Languages address human needs and it s important to keep that in mind Before you do anything else make sure you get IronPython installed on your system and test the installation out using
3. of a line This is the case 1 when no characters have yet been written o standard output 2 gt when the last character written to standard utput is Nn z OF lt 3 when the last write operation on standard utput was not a print statement In some cases it may be ance donee to write an empty string to standard output for this eason ote Objects which act like file objects but which are not the built in file objects often do not properly emulate this aspect of the file object s behavior so it is best not to rely on this n character is written at the end unless the print tatement ends with a comma This is the only action if the statement ontains just the keyword print tandard output is defined as the file object named stdout in the uilt in module sys If no such object exists or if it does not ave a write gt method a RuntimeError exception is raised ae print also has an extended form defined by the second portion of he syntax described above This form is sometimes referred to as lt ypint chevron In this form the first expression after the gt gt must evaluate to a file like object specifically an object hat has a write gt method as described above With this extended orm the subsequent expressions are printed to this file object If he first expression evaluates to None then sys stdout is sed as the
4. you can see everything going on in the background You can also obtain this result by using PYTHONVERBOSE x where x is a True or False environment variable v Prints the version number and exits This option is useful when you want to be sure you re using the correct version of IronPython for your application w arg Defines the kind of warning control Specifying these command line switches tells the interpreter to add the specified warning messages to the output Don t worry too much about these warnings you learn more about them in Chapter 12 You can use any of these values gt Waction Actions are one of the following strings error turns matching warnings into exceptions ignore never prints matching warnings always always prints matching warnings default prints the first occurrence of a warning for each loca tion where the interpreter issues the warning module prints the first occurrence of a warning for each module where the error occurs and once prints only the first occurrence of a warning no matter where it appears gt wmessage Messages are Regular Expressions that define which warning messages to match Wcategory Categories specify the class of the warning message Wmodule Modules are Regular Expressions that define which module to match Wlineno Line numbers are integer values that specify a line number to match Using 0 matches all line numbers x Skips the first line of the s
5. PART Introducing IronPython gt CHAPTER 1 Discovering IronPython gt CHAPTER 2 Understanding the IronPython Basics Discovering IronPython WHAT S IN THIS CHAPTER gt Understanding why you want to add IronPython to your developer toolbox Obtaining and installing IronPython on your machine Understanding some underlying basics of how IronPython works Using IronPython at the console and within a window Yv vyv y Designing and building a simple application IronPython It sounds like some kind of metal snake infesting your computer but it isn t IronPython is the NET version of the open source Python language http www python org Python is a dynamic language that can greatly enhance your programming experience help you create applications in less time and make the applications you create significantly more responsive to user needs Of course you ve heard these promises before from other languages This chapter helps you understand how IronPython delivers on these promises in specific situations The smart developer soon learns that every language serves specific needs and might not work well in others So this chapter isn t here to blow smoke at you once you complete it you ll understand the strengths and weaknesses of IronPython Of course you ll need to obtain a copy of IronPython before you can use it because Visual Studio doesn t include IronPython as part of the default installation This chapter
6. able for def mult a b ownload on return a b print 5 10 print mult 5 10 Just five lines including the blank line between the function and the main code are all you need for this example Functions begin with the def keyword You then give the function a name mult in this case followed by a list of arguments if any a and b for this example Don t worry too much about the details of the IronPython language just yet Part II of the book provides you with a good overview of all the language details As the book progresses you ll be exposed to additional language details By the time you reach the end of the book you ll be working with some relatively com plex examples The content of the function is indented with a tab In this case the function simply returns the value of multiplying a by b Except for the indentation requirement this could easily be a function written in any other language The main code section comes next In this case the code begins by printing 5 10 Notice that you enclose the string values in single quotes The function call ends with an odd looking comma This comma tells the interpreter not to add a n newline character after the print call At this point the code calls print a second time but it calls mult instead of writing text directly The output of mult is an integer which IronPython automatically converts to a string for you and then prints out You
7. ace 20 CHAPTER1 DISCOVERING IRONPYTHON Modifying the IPY EXE Environment Variables IPY also supports a number of environment variables The following list describes each of these environment variables IRONPYTHONPATH Specifies the path to search for modules used within an application IRONPYTHONSTARTUP Specifies the name and location of the startup module Exiting the IronPython Interpreter Eventually you ll want to leave the console In order to end your session simply type exit and press Enter As an alternative you can always press Ctrl Z and then Enter The console will close USING THE IRONPYTHON WINDOWED ENVIRONMENT IronPython Window Console Help IronPython also provides access to a win dowed environment but you can t access it from the start menu Instead you must pro vide a shortcut to the file you want to run or open a command prompt and start the application manually The windowed envi ronment simply provides a GUI interface for working with IronPython but doesn t do anything else for you You start the windowed environment by using IPY W EXE If you type 1Ppyw and press Enter you see the command line switch help shown in Figure 1 9 As you can see from Figure 1 9 the win dowed environment supports the same com mand line switches as the character mode command line version However you can t use the windowed environment to run the interpreted console environment which is a sham
8. activeSession for details gt Full extensibility using the NET Framework gt Complete source code available see http ironpython codeplex com SourceControl ListDownloadableCommits aspx for details One of the negatives of working with IronPython versus Python in the form of CPython is that you lose support for multiple platforms you only have direct access to Windows You can get around this problem using Mono http www mono project com Main_Page but it isn t a straightforward fix and many developers will find it cumbersome Chapter 19 tells you more about working with Mono a valuable solution for some Windows versions as well such as Windows Server 2008 Server Core Of course there isn t any way to get around the lack of Java support you simply choose one virtual machine or the other Appendix A lists more IronPython differences from CPython most of which will cause compatibility and other issues for you Getting IronPython 7 An interesting use of IronPython is as an application testing tool In fact some developers use IronPython exclusively for this purpose Chapter 18 tells you more about this exciting use of IronPython and demonstrates that using IronPython for this purpose really does make application testing considerably easier Don t get the idea that IronPython is going to restrict your use of familiar technologies You can still create a Windows Forms application see Chapter 8 an
9. anced tab of the Computer or My Computer applet 2 Click Environment Variables You ll see an Environment Variables dialog box 3 Highlight Path in the System Variables list Click Edit You ll see the Edit Environment Variable dialog box Using the IronPython Console 15 at IronPython Console elp gt modules lease wait a moment while I gather a list of all available modules aseHTTPServer astion GIHTTPServer onf igParser ookie ockMLRPCServer TMLParser imeWriter ueue impleHTTPServer impleXMLRPCServer ocketServer alendar gi gith nter any module name to get more help or modules whose descriptions contain the word elp gt m collections colorsys commands compileall contextlib cookielib copy copy_reg ctypes datetime decimal difflib dircache is distutils doctest dumbdbn dummy_thread dummy_threading email encodings errno exceptions filecmp fileinput fnmatch formatter f pformat fractions ftplib functools future_builtins gc genericpath getopt getpass gettext glob hashlib heapgq hmac htmlentitydefs htmllib httplib idlelib ihooks imaplib inghdr imp imputil inspect io itertools keyword 1ib2to3 linecache locale logging macpath macurl2path mailbox mailcap markuphase marshal math md5 mhlib mimetools mimet ypes mimif y modulef inder multifile mutex netre new nntplib t n ntpath nturl2path numbers opcode operator optparse os os2emxp
10. and the IronPython environment and what limitations you have when working with IronPython Below this first line you ll see some commands that Microsoft thought you might find useful The Getting Help with Any Function section of the chapter tells you more about the Help command To use the console simply type the commands you want to issue When you re done IronPython will execute the commands and output any result you requested A command need not be a function call or an object instantiation as it is in other languages For example type 2 2 right now and then press Enter You ll see the result of this simple command as shown in Figure 1 4 bv IronPython Console n 2 6 2 6 16920 gt on NET 2 0 50727 3663 gt copyright credits or license for more information FIGURE 1 4 IronPython is dynamic and the console is interactive Whenever you want to end a particular task such as working with Help press Enter a second time The console will take you to the previous level of interaction Getting Help with Any Function You can get help with any function in the console If you simply type help and press Enter in the console IronPython tells you how to request interactive help or help about a specific object To begin interactive help type help and press Enter You ll see the interactive help display shown in Figure 1 5 rype a copyright credits or license for more informat
11. aries from scratch The normal reason to perform this task is to create a special version of IronPython that meets specific needs A company may want to add extensions or special features to IronPython Because you have the source code it s acceptable to create a custom version of IronPython for yourself one that contains any feature set you deem neces sary to get your work completed So have fun molding IronPython and then sharing your modifications with others In order to perform this task you must have a copy of Visual Studio you must have Visual Studio 2010 to Solution Explorer build a DLR version of IronPython The following steps tell fa D you how to build the IronPython 2 6 binaries from scratch o E ll E A Chiron aj Properties 1 Download the source code file such as E References E App config IronPython 2 6 Src zip 2 AppMarifestTemglate ce Chiron cs 2 Extract the files into a folder The example assumes cre32 cs that you extracted the files into the root directory of ee your hard drive into IronPython 2 6 dla 5S HttpSocket cs W Languagelnfo cs 3 Locate the IronPython 2 6 Sre directory and M na open the IronPython sln solution using Visual Studio il sl png o J sk Visual Studio will load the required files and you ll see them in Solution Explorer as shown in Figure 1 2 H XapHttpHandier cs Zip cs Figure 1 2 shows that IronPython consists of a number IronPython of proje
12. asic sys _getframe support X FullFrames Enable sys _getframe with access to locals X GCStress Specifies the GC stress level the generation to collect each statement X LightweightScopes Generate optimized scopes that can be garbage collected X MaxRecursion Set the maximum recursion level X MTA Run in multithreaded apartment X NoAdaptiveCompilation Disable adaptive compilation X PassExceptions Do not catch exceptions that are unhandled by saipt code X PrivateBinding Enable binding to private members X Python30 Enable available Python 3 0 features X ShowCkExceptions Display CLS Exception information X TabCompletion Enable TabCompletion mode X Tracing Enable support for tracing all methods even before sys settrace is called Environment variables TRONPYTHONPATH Path to search for module TRONPYTHONSTARTUP Startup module FIGURE 1 9 The windowed version supports the same features as the command line version Creating Your First Application 21 CREATING YOUR FIRST APPLICATION After all this time you might have started wondering whether you would get to write any code at all in this chapter The first application won t be very fancy but it ll be more than a simple Hello World kind of application You can use any editor that outputs pure text in this section Notepad will work just fine Listing 1 1 shows the code you should type in your editor LISTING 1 1 A simple first application that multiplies two numbers Avail
13. ath pdb pickle pickletools pipes pkgutil platform plistlib popen2 poplib posixfile posixpath pprint profile pstats py_compile pyc lbr pydoc pydoc_topics quopri random re repr rexec rfc822 rlcompleter robot parser runpy sched select sets sgmllib sha shelve shlex shutil site smtpd smtplib sndhdr socket sre_compile sre_constants sre_parse stat statufs string stringold struct sunau sunaudio symbol sys tabnanny tarfile telnetlib tempfile textwrap this thread threading time time it toaiff token tokenize trace traceback types unittest urllib urllib2 urlparse user uu uuid warnings wave weakref whichdb wsgiref xdrlib xml xmllib xmlrpc lib xxsubt ype zipfile Or type modules spam to search FIGURE 1 6 Drill down into help to find topics of interest spam 16 CHAPTER1 DISCOVERING IRONPYTHON IronPython Console ojx 7 print_stmt print Lexpression expression gt i gt gt expression expression gt iD print evaluates each expression in turn and writes the resulting bject to standard output see below If an object is not a string it is first converted to a string using the rules for string onversions The Cresulting or original gt string is then written A pace is written before each object is converted and written unless he output system believes it is positioned at the beginning
14. brary support using hierarchical packages a concept that is already familiar to every NET developer gt Robust third party libraries that support just about every need y Support for writing both extensions and modules in both C and C y Support for writing extensions and modules using third party solutions for both NET IronPython and Java Jython Modular application development Error handling through exceptions another concept familiar to any NET developer High level dynamic data types Ease of embedding within applications as a scripting solution Procedural code that is relatively easy and natural to write Vvv VV V Ease of reading and a clear syntax All these features translate into increased developer productivity which is something that dynamic languages as a whole supposedly provide productivity is one of these issues that is hard to nail down and even harder to prove unless you resort to metrics such as lines of code which prove useless when comparing languages In addition to the great features that Python provides IronPython provides a few of its own The following list provides a brief overview of these features gt Full access to the LNET Framework gt Usability within Silverlight applications gt Interactive console with full dynamic compilation provided as part of the product gt Accessibility from within a browser see http ironpython codeplex com Wiki View aspx title SilverlightInter
15. cts you must compile the entire solution to o a bie aa obtain a workable group of DLLs S iy Compiler O Hosting A O Lib 4 Make any required changes to the source code 2 haiti r r n ij Runtime 5 Choose Build Build Solution Visual Studio E Globalsuppressions cs cH creates the required DLLs ready for testing E a IronPython Modules amp Sa Properties Using Third Party Libraries ay Python is an extremely flexible language and enjoys strong FIGURE 1 2 IronPython consists of third party support In fact you can find lists of these libraries multiple projects so you must compile in various places on the Internet Here are a few places to check the entire solution gt http code google com appengine docs python tools libraries html gt http www amaltas org show third party python libraries and frameworks html gt http dakrauth com blog entry third party python libraries interest IronPython is a complex product If you fail to compile the entire solution every time you make a change you could end up with an unworkable group of DLLs due to interactions It s important to build everything so that any changes propagate properly Understanding the Dynamic Language Runtime 11 You should be able to use some third party libraries with IronPython At the time of this writing you won t actually find any usable third party libraries However you should check http
16. d interact with COM see Chapter 9 It s even possible to create command line console applications see Chapter 10 and work with the Internet see Chapter 11 just as you always have What IronPython provides is another way to view problems that you must address using your applications As with most languages what you re getting is another tool that lets you create solutions in the least amount of time and with the fewest bugs GETTING IRONPYTHON Before you can use IronPython you need to get a copy of your own install it and check to make sure it works Theoretically you might want to obtain the source code and build your own version of IronPython but most developers simply download the binaries and begin working with IronPython right away The first three sections that follow tell you what you need to work with IronPython how to obtain the software and how to install it You ll definitely want to read these sections The final two sections are completely optional In fact you may want to skip them for now and come back to them after you complete more chapters in the book The first optional section tells you how to build your own copy of IronPython from the source The second optional section tells you about third party libraries There s a huge base of third party libraries for IronPython Generally you don t need to install any third party libraries to use this book Everything you need to work with IronPython is included wi
17. e because many developers would prefer working in the nicer environment To see that the windowed environment works the same way as the standard console type IPYW WFDemo py and press Enter You ll see the test application shown earlier in Figure 1 8 IronPython 2 6 2 6 10920 0 on NET 2 0 50727 3082 Type help copyright credits or cense for more information Usage ipy options file py arguments Warn about Python 3 x incompatibiities Program passed in as string terminates option ist Enable application debugging Ignore environment variables Display usage Inspect interactively after running script run library module as a script generate optimized code remove doc strings and apply O optimizations Division options Qold default Qwarn Qwarnall Qnew Don t add user site directory to sys path Don t imply import site on initialization Issue warnings about inconsistent tab usage Tssue errors for inconsistent tab usage Unbuffered stdout amp stderr Verbose trace import statements also PYTHONVERBOSE x Print the version number and exit Warning control arg is action message category module lineno Skip first line of the source X AutoIndent Enable auto indenting in the REPL loop X ColorfulConsole Enable ColorfulConsole X Debug Enable application debugging preferred over D X EnableProfiler Enables profiling support in the compiler X ExceptionDetail Enable ExceptionDetaill mode X Frames Enable b
18. eed to provide IPY EXE with more information about a particular application In this case you can use one of the command line switches shown in the following list to provide IPY EXE with the required information It s important to note that the command line switches are case sensitive v isn t the same as V hale Hello Hello Hello 3 Forces the interpreter to warn about Python 3 com Hello patibility issues in your application c cmd Specifies a command you want to execute This mele command line switch must appear last on the line because anything after this command line switch is interpreted as FIGURE 1 8 The WFDemo shows a command you want to execute For example if you type that you can create windowed ipy c print Hello the interpreter will output environments for IronPython the word Hello applications p Enables application debugging E Ignores any environment variables that you specified as part of the Windows environment variable setup or on the command line after you started it Some applications may not run after you use this command line switch because they won t be able to find modules and other files they need h Displays a complete list of the command line arguments i Displays the console after running the script You can then inspect the results of the script using console commands m module Runs library module as a script o Tells the interpreter to generate optim
19. equire 15MB on you Silverlight C Program Files IronPython 2 6 FIGURE 1 1 Choose the features you want to install When you perform a DLR installation you ll see a Do Not NGen Installed Binaries option on the Custom Setup dialog box Using the Native Image Generator NGen can greatly improve application performance as described at http msdn microsoft com en us magazine cc163610 aspx Earlier versions of IronPython didn t use NGen to build the libraries for you by default You had to use a special command line to obtain the NGen feature msiexec qn i IronPython msi NGENDLLS True The default setup for IronPython 2 6 is to use NGen to build the libraries However using NGen also binds the binaries to the local machine which may not be what you want when working in a dynamic environment Consequently if you plan to use DLR more than you plan to use other IronPython features you might want to check the Do Not NGen Installed Binaries option Select the features you want to install Click Next You ll see a summary dialog box that simply states you re ready to install IronPython Click Install MSI will begin the installation process At some point you ll see an installation completion screen Click Finish You should be ready to begin working with IronPython at this point 10 CHAPTER1 DISCOVERING IRONPYTHON Building the Binaries from Scratch You may eventually want to build the IronPython bin
20. f your sanity the best choice when starting with IronPython is to download the binary version of the product from http ironpython codeplex com Release ProjectReleases aspx ReleaseId 30315 You ll see the Microsoft Installer MSI link right below the Recommended Download link as IronPython 2 6 msi If you really must save the few seconds downloading the MSI version select the IronPython 2 6 Bin zip link instead It s also possible to compile IronPython from the source code If you want to use this option select the IronPython 2 6 Srce zip link You must have a copy of Visual Studio installed on your system to use this option The Building the Binaries from Scratch section of the chapter describes how to build a version from scratch but this process truly isn t for the IronPython beginner and doesn t serve much of a purpose unless you plan to add your own enhancements Most developers will likely use the standard version of IronPython that works with the NET Framework 3 5 and earlier However you might need some of the new features in the NET Framework 4 0 such as the CH dynamic keyword which is part of the Dynamic Language Runtime DLR http dlr codeplex com The section Understanding the Dynamic Language Runtime later in this chapter tells you more about this NET 4 0 feature You can obtain this version of IronPython at http ironpython codeplex com Release ProjectReleases aspx ReleaseId 27320 The examples i
21. file for output gt gt z FIGURE 1 7 The console also provides the means to obtain precise help about any module keyword or topic 4 Select the end of the string that appears in the Variable Value field Type C Program Files IronPython 2 6 and click OK Make sure you modify this path to match your IronPython configuration 5 Click OK three times to close the Edit System Variable Environment Variables and System Properties dialog boxes When you open a command prompt you ll be able to access the IronPython executables Executing an Application from the Command Prompt Normally you execute an application by typing IPY lt Python Filename gt and pressing Enter Give it a try now Open a command prompt type cD Program Files IronPython 2 6 Tutorial and press Enter You re in the sample files supplied by IronPython Type IPY wFDemo py and press Enter You ll see a window displayed When you click your mouse in the window you see the word Hello Using the IronPython Console 17 displayed at each click point as shown in Figure 1 8 If you look at the command prompt window at this point you ll see that the mouse cursor is blinking but you can t type anything because the com mand prompt is waiting for the IronPython interpreter to end When you click the Close button the application ends and you can again type something at the command prompt Understanding the IPY EXE Standard Command Line Switches Sometimes you n
22. g Python and by extension IronPython is batteries included Python has an immense standard library that addresses everything from working with ZIP files to interacting with the file system You ll discover the details of working with the Standard Library in Chapter 6 For now it s important to know that the Standard Library has a lot to offer and you may very well be able to build many of your applications without ever thinking about the NET Framework As previously mentioned IronPython is a NET version of the Python language For a NET developer using IronPython has the advantage of letting you create extensions using NET see Chapters 16 and 17 for details In addition you have full access to the NET Framework see Chapter 7 for details You can work with IronPython and other NET languages that you already know which means that you can use the right tool for every job However IronPython has a few differences from the CPython implementation that everyone else uses see Appendix A for details which means that you can occa sionally run into some odd compatibility problems when using IronPython As with most things in life advantages usually come with a few disadvantages You ll see Python appear in many guises when you begin using it The original implementation of Python is CPython and that s the implementation that most developers target In fact you ll often see IronPython compared and contrasted with CPython throughou
23. helps you get IronPython installed on your system and tells you about some options you may want to install as well Once you have IronPython installed you ll want to know a little about how it works This chapter won t make you an IronPython guru who s familiar with every nuance of the underlying structural elements but it will give you a good overview that will make the rest of the book a lot easier to understand You ll put your new found knowledge to the test by performing a few tasks at the IronPython console and within the IronPython windowed environment 4 CHAPTER1 DISCOVERING IRONPYTHON Finally this chapter takes you through the process of creating a simple application No this isn t going to be the next great Windows application It will be a little better than Hello World but not much The idea is to get you started doing something useful with IronPython Don t worry the examples will become a lot more interesting as the book progresses AN OVERVIEW OF IRONPYTHON It surprises many developers to discover that computer languages are for humans not for computers A computer couldn t care less about which language you use because it s all bits and bytes in the end anyway Consequently when you decide to learn another computer language it really does pay to know what that language will do for you the developer Otherwise there really isn t a point in making the effort One phrase you often hear when discussin
24. ility because IronPython applications are so flexible Dynamic languages provide a number of benefits such as the ability to enter several statements and execute them immediately to obtain feedback Using a dynamic language also provides easier refactoring and code modification because you don t have to change static definitions throughout your code It s even possible to call functions you haven t implemented yet and add an implementa tion later in the code when it s needed Don t get the idea that dynamic languages are new In fact dynamic languages have been around for a very long time Examples of other dynamic languages include the following gt LISP List Processing Smalltalk JavaScript PHP Ruby ColdFusion Lua Cobra Vv YV VY VV YV Groovy Developers also assign a number of advantages specifically to the Python language and IronPython s implementation of it Whether these features truly are advantages to you depends on your perspective and experience Many people do agree that Python provides these features Support for the Windows Linux Unix and Mac OS X platforms Managed support using both Java and NET Considerable object oriented programming OOP functionality that is easy to understand and use gt The capability to look within the code NET developers will know this as a strong form of reflection 6 CHAPTER1 DISCOVERING IRONPYTHON An extensive array of standard libraries Full li
25. ion elp ype help lt gt for interactive help or help lt object gt for help about object gt gt gt help lt gt elcome to Python 2 6 This is the online help utility If this is your first time using Python you should definitely check out he tutorial on the Internet at http docs python org tutorial nter the name of any module keyword or topic to get help on writing ython programs and using Python modules To quit this help utility and eturn to the interpreter just type quit o get a list of available modules keywords or topics type modules keywords or topics Each module also comes with a one line summary f what it does to list the modules whose summaries contain a given word uch as spam type modules spam elp gt FIGURE 1 5 Interactive help lets you ask questions about IronPython 14 CHAPTER1 DISCOVERING IRONPYTHON Let s say you have no idea of what you want to find Console help provides you with a list of words you can type to get general help These terms are gt Modules Keywords gt Topics Type any of these terms and press Enter You ll see a list of additional words you can type as shown in Figure 1 6 for modules Using this technique you can drill down into help and locate anything you want In fact it s a good idea to spend some time in help just to see what s available Even advanced developers can benefit from this approach I personally follow th
26. is approach when I have time to increase my level of knowledge about all of the languages I use IronPython will constantly refer you to the online help for Python So you might as well check it out now You ll find a good Python tutorial at http docs python org tutorial While you re at it there s also a good TronPython specific tutorial that comes with your installation Simply choose Start Programs IronPython 2 6 IronPython Tutorial Although these sources of help are useful you ll get a much better start working through the examples in the book You might know about the topic you want to find For example you might know that you want to print something to screen but you don t quite know how to use print In this case type help print and press Enter Figure 1 7 shows the results You see complete documentation about the print keyword Understanding the IPY EXE Command Line Syntax When you open a console window what you re actually doing is executing IPY EXE which is the IronPython interpreter You don t have to open a console window to use IPY EXE In fact you normally won t It s possible to execute IronPython applications directly at the command line The following sections discuss IPY EXE in more detail Adding IPY EXE to the Windows Environment Before you can use IPY EXE effectively you need to add it to the Windows path statement The following steps provide a brief procedure 1 Open the Adv
27. ized code which means you can t perform debugging but the application will run faster oo Removes all of the doc strings and applies o optimizations so that the application runs even faster than using the o command line switch alone Q arg Specifies use of one of several division options You can use any of these values gt Qold default The precision of the output depends on the operators used For example if you divide two integers you get an integer as output gt Qwarn Outputs warnings about a loss of precision when performing division using integers gt Qwarnall Outputs warnings about all uses of the classic division operator gt Qnew The output is always a precise floating point fraction 18 CHAPTER1 DISCOVERING IRONPYTHON s Specifies that the interpreter shouldn t add the user site directory to sys path s Specifies that the interpreter shouldn t imply that it should execute the import site command on initialization t Outputs warnings about inconsistent tab usage which can lead to code interpretation problems tt Outputs errors for inconsistent tab usage Inconsistent tab usage can lead to code interpretation problems which can result in hard to locate bugs u Provides unbuffered stdout and stderr devices Typically the interpreter uses buffering to provide better application performance v Specifies that the interpreter should provide verbose output which means that
28. m out and then work out additional details without too many consequences In addition because the console is interactive you obtain immediate feedback so you don t have to wait for a compile cycle to discover that something you re doing is completely wrong In fact even after you ve mastered IronPython you ll find that you use the console to try things out Because IronPython is a dynamic language you can try things without worrying about damaging an applica tion You can test things quickly using the console and then include them in your application The following sections describe the IronPython console and how to use it Expect to see the IronPython console in future chapters Opening and Using the Default Console The IronPython console is an application provided with the default installation You access it using the Start gt Programs IronPython 2 6 IronPython Console command The console shown in Figure 1 3 looks something like a command prompt but it isn t IronPython Console n 2 6 2 6 16920 gt on NET 2 6 56727 3682 gt copyright credits or license for more information FIGURE 1 3 The IronPython console looks something like a command prompt Using the IronPython Console 13 Notice that the top of the window tells you which version of IronPython you re using and which version of the NET Framework it s running on This is important information because it helps you underst
29. n this book will work with either version of IronPython 2 6 except where noted where I m demonstrating how to work with the DLR Performing the Installation This section assumes that you ve downloaded the MSI file to make life easy for yourself This pro cedure works equally well for either version of IronPython 2 6 so you can use it for a DLR install as well The following instructions help you get IronPython installed on your machine 1 Double click the MSI file you downloaded from the CodePlex Web site You ll see the usual Welcome page click Next to get past it Getting IronPython 9 Read the licensing agreement check I Accept the Terms in the License Agreement and then click Next You ll see the Custom Setup dialog box shown in Figure 1 1 where you can select the IronPython features you want to install At a minimum you must install the Runtime The Documentation Standard Library and Tools features are also strongly recommended This book assumes that you ve installed all the features However you might want to install just those features you actually need for a production setup you might not actually need the samples ig IronPython 2 6 Setup Custom Setup Select the way you want features to be installed Click the icons in the tree below to change the way features will be installed This feature requires OKB on your sewers hard drive Ithas 6 of 6 Tools subfeatures selected The subfeatures r
30. ource code which may have special instructions that you don t need for the current session IronPython doesn t support all of the CPython command line switches Consequently you may find that a batch file written to execute a CPython application won t work properly with IronPython For example IronPython doesn t appear to support the PYTHONHOME environment variable All IronPython environment variables begin with IRON so you need to modify batch files to include this first word as part of any environmental variable setup Using the IronPython Console 19 Working with the X Command Line Switches In addition to the standard command line switches you also have access to the X command line switches which configure the IronPython interpreter The following list describes each of the con figuration options X AutoIndent Enables auto indenting in the read evaluation print loop REPL X Colorfulconsole Enables ColorfulConsole support X Debug Enables application debugging This option is preferred over the D command line switch because it s newer and will enjoy a longer support period X EnableProfiler Enables profiling support in the compiler which helps you optimize your applications X ExceptionDetail Enables ExceptionDetail mode which gives you more information about every exception that occurs making it easier to locate the source of the problem but filling the screen much faster as well
31. t this book It s important to remember that all these implementations attempt to achieve the same goal full support of the Python standard In most cases all you really need to worry about is the IronPython implementation unless you plan to use third party libraries written for another Python implementation This book helps you understand the use of CPython extensions in Appendix B There are some basic reasons that you want to use IronPython or Python for that matter The most important reason is that IronPython is a dynamic language which means that it performs many tasks during run time rather than compile time Using a dynamic language means that your code has advantages of static languages such as Visual Basic in that it can more easily adapt to changing An Overview of IronPython 5 environmental conditions You ll discover many other dynamic language advantages as the chapter progresses Unfortunately you often pay for runtime flexibility with poorer performance there s always a tradeoff between flexibility and performance Performance is a combination of three factors speed reliability and security When an application has a performance hit it means a decrease in any of these three factors When working with IronPython there is a decrease in speed because the interpreter must compile code at run time rather than at compile time This speed decrease is partially offset by an improvement in reliab
32. ter 14 Consequently you can begin accessing these features immediately when using Visual Studio 2010 without having to install any additional support Microsoft currently supports these lan guages using DLR gt IronPython gt IronRuby gt JavaScript EcmaScript 3 0 gt Visual Basic Silverlight also provides support for DLR and there s even a special SDK for Silverlight DLR You can dis cover more about this SDK at http silverlight net learn dynamic languages The relevance of Silverlight support for this book is that you can now use IronPython as part of your Silverlight solution as described in Chapter 11 You can summarize the benefits of using DLR as follows gt Makes it easier to port dynamic languages to the NET Framework gt Lets you include dynamic features in static languages 12 CHAPTER1 DISCOVERING IRONPYTHON Creates an environment where sharing of objects and libraries between languages is possible gt Makes it possible to perform fast dynamic dispatch and invocation of objects This section provides a good overview of DLR You ll discover additional details about DLR as the book progresses However if you d like to delve into some of the architectural details of DLR check out the article at http msdn microsoft com library dd233052 aspx USING THE IRONPYTHON CONSOLE The IronPython console is the best place to begin working with IronPython You can enter a few statements test the
33. th the download you get from the CodePlex Web site The only time you might need to work with third party libraries is in Part IV You ll receive specific instructions in the Part IV chapters for any required third party libraries so you only need to read Using Third Party Libraries if you plan to work with third party libraries immediately Understanding the IronPython Requirements As with any software IronPython has basic system requirements you must meet before you can use it It turns out that there are actually two versions of IronPython 2 6 one for the NET Framework 2 0 3 0 and 3 5 and a second for the NET Framework 4 0 Here are the requirements for the NET Framework 2 0 3 0 and 3 5 version gt The NET Framework 2 0 3 0 and 3 5 8 CHAPTER1 DISCOVERING IRONPYTHON gt Optional Visual Studio 2005 or Visual Studio 2008 your system must meet the prerequi sites for this software gt Optional NET Framework 2 0 Software Development Kit SDK You need only the optional requirements if you plan to build IronPython 2 6 from the source code Here are the requirements for the NET Framework 4 0 version again the optional requirements are there if you want to build IronPython from source code gt The NET Framework 4 0 gt Optional Visual Studio 2010 Getting the Software As with most open source software you have a number of choices when it comes to download ing IronPython For the sake o
34. the examples in this chapter If you re getting some weird result or nothing at all you might have a bad installation Once you know that you do have a good installation try playing around with the example application in the Creating Your First Application section of the chapter Work with this application as a means of working with the tools discussed in the Using the IronPython Console and Using the IronPython Windowed Environment sections of the chapter At this point you really don t know too much about the Python language or the IronPython implemen tation of that language However you probably do know something about other NET languages and that s a good starting point Chapter 2 builds on the information you ve learned in this chapter and also builds on your personal knowledge of the NET Framework In Chapter 2 you begin building knowl edge about IronPython so you can see what an interesting language it is and so you can also begin to understand the example in the Creating Your First Application section of the chapter When you get done with Chapter 2 you may want to take another look at the sample application you ll be sur prised to discover that you really do know how the example works
35. www ironpython info index php Third Party_Library_Compatibility from time to time to dis cover whether there are any third party libraries that do work with IronPython It s important to note that this list represents only tested libraries you may find other third party libraries that do work with the current version of IronPython UNDERSTANDING THE DYNAMIC LANGUAGE RUNTIME IronPython is a dynamic language yet the Common Language Runtime CLR is a static environ ment While you can build a compiler that makes it possible to use a dynamic language with CLR as was done for IronPython 1 0 you ll find that certain functionality is missing because CLR simply doesn t understand dynamic languages Consequently Microsoft started the Dynamic Language Runtime DLR project see http dlr codeplex com for additional information DLR sits on top of CLR and performs a level of interpretation that offers additional functionality for dynamic languages By relying on DLR IronPython gains access to the following support gt Shared dynamic type support Shared hosted model Quick dynamic code generation Interaction with other dynamic languages Vv vv y Improved interaction with static languages such as C and Visual Basic NET see Chapters 15 16 and 17 for details gt Shared sandbox security model and browse integration DLR is now part of the NET Framework 4 0 In fact you ll discover the details of this integration in Chap
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