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2.2 A walk through the example

Lines 20-24 are the Cheetah-specific imports. Line 33 introduces our generated class, `x`, a subclass of `Template`. It's called x because the source file was x.tmpl.

Lines 40-46 are the `.__init__` method called when the template is instantiated or used as a Webware servlet, or when the module is run as a standalone program. We can see it calling its superclass constructor and setting `._filePath` and `._fileMtime` to the filename and modification time (in Unix ticks) of the source .tmpl file.

Lines 47-84 are the main method `.respond`, the one that fills the template. Normally you call it without arguments, but Webware calls it with a Webware `Transaction` object representing the current request. Lines 57-59 set up the `trans` variable. If a real or dummy transaction is passed in, the method uses it. Otherwise (if the `trans` argument is `None`), the method creates a `DummyTransaction` instance. `dummyTrans` is a flag that just tells whether a dummy transaction is in effect; it'll be used at the end of the method.

The other four `.respond` arguments aren't anything you'd ever want to pass in; they exist solely to speed up access to these frequently-used global functions. This is a standard Python trick described in question 4.7 of the Python FAQ (http://www.python.org/cgi-bin/faqw.py). `VFS` and `VFN` are the functions that give your template the benefits of NameMapper lookup, such as the ability to use the searchList.

Line 60 initializes the `write` variable. This important variable is discussed below.

Lines 60-63 initialize a few more local variables. `SL` is the searchList. `filter` is the current output filter. `globalSetVars` are the variables that have been defined with `#set global`.

The comments at lines 65 and 78 delimit the start and end of the code that varies with each template. The code outside this region is identical in all template modules. That's not quite true - `#import` for instance generates additional `import` statements at the top of the module - but it's true enough for the most part.

Lines 68-74 exist only if the template source was a named file rather than a string or file object. The stanza recompiles the template if the source file has changed. Lines 70-74 seem to be redundant with 75-83: both fill the template and send the output. The reason the first set of lines exists is because the second set may become invalid when the template is recompiled. (This is for re compilation only. The initial compilation happened in the `.__init__` method if the template wasn't precompiled.)

Line 75 is the most interesting line in this module. It's a direct translation of what we put in the template definition, ``Hello, world!'' Here the content is a single string literal. `write` looks like an ordinary function call, but remember that line 60 made it an alias to `trans.response().write`, a method in the transaction. The next few chapters describe how the different placeholders and directives influence this portion of the generated class.

Lines 80-83 finish the template filling. If `trans` is a real Webware transaction, `write` has already sent the output to Webware for handling, so we return `""`. If `trans` is a dummy transaction, `write` has been accumulating the output in a Python `StringIO` object rather than sending it anywhere, so we have to return it.

Line 83 is the end of the `.respond` method.

Line 87 makes code.__str__ an alias for the main method, so that you can `print` it or apply `str` to it and it will fill the template. Line 88 gives the name of the main method, because sometimes it's not `.respond`.

Lines 94-95 allow the module to be run directly as a script. Essentially, they process the command-line arguments and them make the template fill itself.