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| author | Jack Jansen <jack.jansen@cwi.nl> | 1996-07-18 16:07:05 (GMT) |
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| committer | Jack Jansen <jack.jansen@cwi.nl> | 1996-07-18 16:07:05 (GMT) |
| commit | 024a387f89cd4c08b67ffca0d8df311a34cc8a49 (patch) | |
| tree | c1ec0a777e2c6b02596ddeb54cdb0e3fa7e02653 /Mac/Demo/example0.html | |
| parent | a547dcaff09fa530871a0405b146c6bf958b48b4 (diff) | |
| download | cpython-024a387f89cd4c08b67ffca0d8df311a34cc8a49.zip cpython-024a387f89cd4c08b67ffca0d8df311a34cc8a49.tar.gz cpython-024a387f89cd4c08b67ffca0d8df311a34cc8a49.tar.bz2 | |
- Added a file dialog example
- Added pointers to library documentation
Diffstat (limited to 'Mac/Demo/example0.html')
| -rw-r--r-- | Mac/Demo/example0.html | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/Mac/Demo/example0.html b/Mac/Demo/example0.html new file mode 100644 index 0000000..c0336a5 --- /dev/null +++ b/Mac/Demo/example0.html @@ -0,0 +1,75 @@ +<HTML><HEAD><TITLE>Using python to create Macintosh applications, part zero</TITLE></HEAD> +<BODY> +<H1>Using python to create Macintosh applications, part zero</H1> +<HR> + +This document will show you how to create a simple mac-style +application using Python. We will glance at how to use file dialogs and +messages. <p> + +Our example program <a href="example0/checktext.py">checktext.py</a> asks +the user for a text file and checks what style end-of-lines the file has. +This may need a little explanation: ASCII text files are almost identical +on different machines, with one exception: +<ul> +<li> Unix systems terminate lines with the "linefeed" character, <code>0x0a</code>, +<li> Macintoshes terminate lines with the "carriage return" character, +<code>0x0d</code> and +<li> MSDOS systems terminate lines with first a carriage return and then a linefeed. +</ul> + +Let us have a look at the program. The first interesting statement in the main +program is the call to <code>macfs.PromptGetFile</code>. This is one of the routines +that allow you to ask the user to specify a file. You pass it one required +argument, the prompt string. There are up to four optional MacOS <em>file type</em> arguments +you can pass, as 4-byte strings. Specifying no file +type will allow the user to select any file, specifying one or more types restricts +the user to files of this type. File types are explained in most books on the Mac. <p> + +<code>PromptGetFile</code> returns two values: an <em>FSSpec</em> object and a +success indicator. The FSSpec object is the "official" MacOS way of specifying a +file, more on it later. The success indicator tells you whether the user clicked OK +or Cancel. In the event of Cancel we simply exit back to the finder. <p> + +<code>PromptGetFile</code> has a number of friends that do similar things: +<ul> +<li> <code>StandardGetFile</code> is identical to <code>PromptGetFile</code> but +without the prompt. It has up to four optional filetype arguments. +<li> <code>StandardPutFile</code> asks the user for an output file. It will +warn the user when she tries to overwrite an existing file. The routine has one +mandatory argument: a prompt string. Pass the empty string if you do not want a prompt. +<li> <code>GetDirectory</code> asks the user for a folder (or directory, in unix terms). +It has one optional argument: a prompt string. +</ul> +All routines return an FSSpec and a success indicator. <p> + +There are many things you can do with FSSpec objects (see the +<a href="http://www.python.org/doc/lib/macfs.html">macfs</a> section in the +<a href="http://www.python.org/doc/lib/Top.html">Python Library Reference</a> +for details), but passing them to <code>open</code> is not +one of them. For this, we first have to convert the FSSpec object to a pathname, with +the <code>as_pathname</code> method. This returns a standard MacOS-style pathname with +colon-separated components. This can then be passed to <code>open</code>. Note that +we call open with mode parameter <code>'rb'</code>: we want to read the file in binary +mode. Python, like C and C++, uses unix-style line endings internally and opening a +file in text mode (<code>'r'</code>) would result in conversion of carriage-returns to +linefeeds upon reading. This is something that Mac and DOS programmers are usually aware +of but that never ceases to amaze unix buffs. <p> + +After we open the file we attempt to read all data into memory. If this fails we use +<code>EasyDialogs.Message</code> to display a message in a standard dialog box and exit. +The EasyDialogs module has a few more useful simple dialog routines, more on that in +<a href="example1.html">example 1</a>. <p> + +The rest of the code is pretty straightforward: we check that the file actually contains +data, count the number of linefeeds and returns and display a message with our guess of the +end-of-line convention used in the file. <p> + +The <a href="example0">example0</a> folder has three text files in Mac, Unix and DOS style +for you to try the program on. After that, you can continue with <a href="example1.html">example 1</a> +or go back to the <a href="index.html">index</a> to find another interesting topic. <p> + +<HR> +<A HREF="http://www.cwi.nl/~jack">Jack Jansen</A>, +<A HREF="mailto:jack@cwi.nl">jack@cwi.nl</A>, 18-July-1996. +</BODY></HTML> |