| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 1 | <HTML><HEAD><TITLE>Using Open Scripting Extension from Python</TITLE></HEAD> |
| 2 | <BODY> |
| 3 | <H1>Using Open Scripting Extension from Python</H1> |
| 4 | <HR> |
| 5 | |
| 6 | OSA support in Python is still far from complete, and what |
| 7 | support there is is likely to change in the forseeable future. Still, |
| 8 | there is already enough in place to allow you to do some nifty things |
| 9 | to other programs from your python program. <P> |
| 10 | |
| 11 | <CITE> |
| 12 | Actually, when we say "AppleScript" in this document we actually mean |
| 13 | "the Open Scripting Architecture", there is nothing |
| 14 | AppleScript-specific in the Python implementation. <p> |
| 15 | </CITE> |
| 16 | |
| 17 | In this example, we will look at a scriptable application, extract its |
| 18 | "AppleScript Dictionary" and generate a Python interface module from |
| 19 | that and use that module to control the application. Because we want |
| 20 | to concentrate on the OSA details we don't bother with a real |
| 21 | user-interface for our application. <p> |
| 22 | |
| 23 | The application we are going to script is Eudora Light, a free mail |
| 24 | program from <A HREF="http://www.qualcomm.com">QualComm</A>. This is a |
| 25 | very versatile mail-reader, and QualComm has an accompanying |
| 26 | commercial version once your needs outgrow Eudora Light. Our program |
| 27 | will tell Eudora to send queued mail, retrieve mail or quit. <p> |
| 28 | |
| 29 | <H2>Creating the Python interface module</H2> |
| 30 | |
| 31 | There is a tool in the standard distribution that looks through a file |
| 32 | for an 'AETE' or 'AEUT' resource, the internal representation of the |
| 33 | AppleScript dictionary. This tool is called |
| Jack Jansen | f10786b | 1997-08-19 14:00:56 +0000 | [diff] [blame^] | 34 | <CODE>gensuitemodule.py</CODE>, and lives in <CODE>Mac:scripts</CODE>. |
| 35 | When we start it, it asks us for an input file and we point it to the |
| 36 | Eudora Light executable. It starts parsing the AETE resource, and for |
| 37 | each AppleEvent suite it finds it prompts us for the filename of the |
| 38 | resulting python module. Remember to change folders for the first |
| 39 | module, you don't want to clutter up the Eudora folder with your python |
| 40 | interfaces. If you want to skip a suite you press cancel and the process |
| 41 | continues with the next suite. In the case of Eudora, you do |
| 42 | <EM>not</EM> want to generate the Required and Standard suites, because |
| 43 | they are identical to the standard ones which are pregenerated (and |
| 44 | empty in the eudora binary). AppleScript understands that an empty suite |
| 45 | means "incorporate the whole standard suite by this name", |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 46 | gensuitemodule does not currently understand this. Creating the empty |
| 47 | <CODE>Required_Suite.py</CODE> would hide the correct module of that |
| 48 | name from our application. <p> |
| 49 | |
| Jack Jansen | f10786b | 1997-08-19 14:00:56 +0000 | [diff] [blame^] | 50 | Gensuitemodule may ask you questions like "Where is enum 'xyz ' declared?". |
| 51 | For the first time, cancel out of this dialog after taking down the |
| 52 | enum (or class or prop) name. After you've created all the suites look |
| 53 | for these codes, in the suites generated here and in the standard suites. |
| 54 | If you've found them all run gensuitemodule again and point it to the right |
| 55 | file for each declaration. Gensuitemodule will generate the imports to make the |
| 56 | reference work. <p> |
| 57 | |
| Jack Jansen | 0836542 | 1996-04-19 15:56:08 +0000 | [diff] [blame] | 58 | <BLOCKQUOTE> |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 59 | Time for a sidebar. If you want to re-create |
| 60 | <CODE>Required_Suite.py</CODE> or one of the other standard modules |
| 61 | you should look in <CODE>System Folder:Extensions:Scripting |
| 62 | Additions:Dialects:English Dialect</CODE>, that is where the core |
| 63 | AppleEvent dictionaries live. Also, if you are looking for the |
| 64 | <CODE>Finder_Suite</CODE> interface: don't look in the finder (it has |
| 65 | an old System 7.0 scripting suite), look at the extension <CODE>Finder |
| 66 | Scripting Extension</CODE>. <p> |
| Jack Jansen | 0836542 | 1996-04-19 15:56:08 +0000 | [diff] [blame] | 67 | </BLOCKQUOTE> |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 68 | |
| 69 | Let's glance at the <A |
| 70 | HREF="scripting/Eudora_Suite.py">Eudora_Suite.py</A> just created. You |
| 71 | may want to open Script Editor alongside, and have a look at how it |
| 72 | interprets the dictionary. EudoraSuite.py starts with some |
| Jack Jansen | f10786b | 1997-08-19 14:00:56 +0000 | [diff] [blame^] | 73 | boilerplate, then a big class definition with methods for each |
| 74 | AppleScript Verb, then some small class definitions and then some dictionary |
| 75 | initializations. <p> |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 76 | |
| 77 | The <CODE>Eudora_Suite</CODE> class is the bulk of the code |
| 78 | generated. For each verb it contains a method. Each method knows what |
| 79 | arguments the verb expects, and it makes handy use of the keyword |
| 80 | argument scheme introduced in Python 1.3 to present a palatable |
| 81 | interface to the python programmer. You will see that each method |
| 82 | calls some routines from <CODE>aetools</CODE>, an auxiliary module |
| Jack Jansen | 0836542 | 1996-04-19 15:56:08 +0000 | [diff] [blame] | 83 | living in <CODE>Lib:toolbox</CODE> which contains some other nifty |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 84 | AppleEvent tools as well. Have a look at it sometime, there is (of |
| 85 | course) no documentation yet. <p> |
| 86 | |
| 87 | The other thing you notice is that each method calls |
| 88 | <CODE>self.send</CODE>, but no such method is defined. You will have |
| 89 | to provide it by subclassing or multiple inheritance, as we shall see |
| 90 | later. <p> |
| 91 | |
| Jack Jansen | f10786b | 1997-08-19 14:00:56 +0000 | [diff] [blame^] | 92 | After the big class we get a number of little class declarations. These |
| 93 | declarations are for the (appleevent) classes and properties in the suite. |
| 94 | They allow you to create object IDs, which can then be passed to the verbs. |
| 95 | For instance, to get the name of the sender of the first message in mailbox |
| 96 | inbox you would use <code>mailbox("inbox").message(1).sender</code>. It is |
| 97 | also possible to specify this as <code>sender(message(1, mailbox("inbox")))</code>, |
| 98 | which is sometimes needed because these classes don't inherit correctly |
| 99 | from baseclasses, so you may have to use a class or property from another suite. <p> |
| 100 | |
| 101 | <blockquote> |
| 102 | There are also some older object specifiers for standard objects in aetools. |
| 103 | You use these in the form <CODE>aetools.Word(10, |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 104 | aetools.Document(1))</CODE> where the corresponding AppleScript |
| 105 | terminology would be <CODE>word 10 of the first |
| 106 | document</CODE>. Examine the two modules mentioned above along with |
| 107 | the comments at the end of your suite module if you need to create |
| Jack Jansen | f10786b | 1997-08-19 14:00:56 +0000 | [diff] [blame^] | 108 | more than the standard object specifiers. |
| 109 | </blockquote> |
| 110 | |
| 111 | Next we get the enumeration dictionaries, which allow you to pass |
| 112 | english names as arguments to verbs, so you don't have to bother with the 4-letter |
| 113 | type code. So, you can say |
| 114 | <CODE><PRE> |
| 115 | eudora.notice(occurrence="mail_arrives") |
| 116 | </PRE></CODE> |
| 117 | instead of the rather more cryptic |
| 118 | <CODE><PRE> |
| 119 | eudora.notice(occurrence="wArv") |
| 120 | </PRE></CODE><p> |
| 121 | |
| 122 | Finally, we get the "table of contents" of the module, listing all classes and such |
| 123 | by code, which is used by gensuitemodule. <p> |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 124 | |
| 125 | <H2>Using a Python suite module</H2> |
| 126 | |
| 127 | Now that we have created the suite module we can use it in an |
| 128 | application. We do this by creating a class that inherits |
| 129 | <CODE>Eudora_Suite</CODE> and the <CODE>TalkTo</CODE> class from |
| 130 | <CODE>aetools</CODE>. The <CODE>TalkTo</CODE> class is basically a |
| 131 | container for the <CODE>send</CODE> method used by the methods from |
| 132 | the suite classes. <p> |
| 133 | |
| 134 | Actually, our class will also inherit <CODE>Required_Suite</CODE>, |
| 135 | because we also need functionality from that suite: the quit |
| 136 | command. Gensuitemodule could have created this completely derived |
| 137 | class for us, since it has access to all information needed to build |
| 138 | the class but unfortunately it does not do so at the moment. All in |
| 139 | all, the heart of our program looks like this: |
| 140 | <CODE><PRE> |
| 141 | import Eudora_Suite, Required_Suite, aetools |
| 142 | |
| Jack Jansen | f10786b | 1997-08-19 14:00:56 +0000 | [diff] [blame^] | 143 | class Eudora(Eudora_Suite.Eudora_Suite, Required_Suite.Required_Suite, \ |
| 144 | aetools.TalkTo): |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 145 | pass |
| 146 | </PRE></CODE> |
| 147 | |
| 148 | Yes, our class body is <CODE>pass</CODE>, all functionality is already |
| 149 | provided by the base classes, the only thing we have to do is glue it |
| 150 | together in the right way. <p> |
| 151 | |
| 152 | Looking at the sourcefile <A |
| 153 | HREF="scripting/testeudora.py">testeudora.py</A> we see that it starts |
| Jack Jansen | 0836542 | 1996-04-19 15:56:08 +0000 | [diff] [blame] | 154 | with some imports. Then we get the class definition |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 155 | for our main object and a constant giving the signature of Eudora. <p> |
| 156 | |
| 157 | This, again, needs a little explanation. There are various ways to |
| 158 | describe to AppleScript which program we want to talk to, but the |
| 159 | easiest one to use (from Python, at least) is creator |
| 160 | signature. Application name would be much nicer, but Python currently |
| 161 | does not have a module that interfaces to the Finder database (which |
| 162 | would allow us to map names to signatures). The other alternative, |
| 163 | <CODE>ChooseApplication</CODE> from the program-to-program toolbox, is |
| 164 | also not available from Python at the moment. <p> |
| 165 | |
| Jack Jansen | bdf03a0 | 1996-09-20 15:22:47 +0000 | [diff] [blame] | 166 | If you specify the application by creator you can specify an optional |
| 167 | <CODE>start</CODE> parameter, which will cause the application to be |
| 168 | started if it is not running. <P> |
| 169 | |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 170 | The main program itself is a wonder of simplicity. We create the |
| 171 | object that talks to Eudora (passing the signature as argument), ask |
| 172 | the user what she wants and call the appropriate method of the talker |
| 173 | object. The use of keyword arguments with the same names as used by |
| 174 | AppleScript make passing the parameters a breeze. <p> |
| 175 | |
| 176 | The exception handling does need a few comments, though. Since |
| 177 | AppleScript is basically a connectionless RPC protocol nothing happens |
| 178 | when we create to talker object. Hence, if the destination application |
| 179 | is not running we will not notice until we send our first |
| 180 | command. There is another thing to note about errors returned by |
| Jack Jansen | 0fb1d82 | 1996-11-20 15:13:24 +0000 | [diff] [blame] | 181 | AppleScript calls: <CODE>MacOS.Error</CODE> is raised for |
| 182 | all of the errors that are known to be <CODE>OSErr</CODE>-type errors, |
| 183 | server generated errors raise <CODE>aetools.Error</CODE>. <p> |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 184 | |
| Jack Jansen | a742d11 | 1996-12-23 17:28:53 +0000 | [diff] [blame] | 185 | <H2>Scripting Additions</H2> |
| 186 | |
| 187 | If you want to use any of the scripting additions (or OSAXen, in |
| 188 | everyday speech) from a Python program you can use the same method |
| 189 | as for applications, i.e. run <CODE>gensuitemodule</CODE> on the |
| 190 | OSAX (commonly found in <CODE>System Folder:Extensions:Scripting Additions</CODE> |
| 191 | or something similar), define a class which inherits the generated |
| 192 | class and <CODE>aetools.TalkTo</CODE> and instantiate it. The application |
| 193 | signature to use is <CODE>'MACS'</CODE>. <P> |
| 194 | |
| 195 | There are two minor points to watch out for when using gensuitemodule |
| 196 | on OSAXen: they appear all to define the class <CODE>System_Object_Suite</CODE>, |
| 197 | and a lot of them have the command set in multiple dialects. You have to |
| 198 | watch out for name conflicts, so, and make sure you select a reasonable dialect |
| 199 | (some of the non-english dialects cause gensuitemodule to generate incorrect |
| 200 | Python code). <P> |
| 201 | |
| Jack Jansen | a630813 | 1996-03-18 13:38:52 +0000 | [diff] [blame] | 202 | That concludes our simple example. Again, let me emphasize that |
| 203 | scripting support in Python is not very complete at the moment, and |
| 204 | the details of how to use AppleEvents will definitely change in the |
| 205 | near future. This will not only fix all the ideosyncracies noted in |
| 206 | this document but also break existing programs, since the current |
| 207 | suite organization will have to change to fix some of the problems. |
| 208 | Still, if you want to experiment with AppleEvents right now: go ahead! |
| 209 | <p> |