Table of Contents

PEAK API Reference  

Fixes and Enhancements since Version 0.5 alpha 3

  • peak.running.options is now a thin wrapper over peak.cli.options, from the separately-distributed CLI-Tools package

  • Added "paramstyle" support for SQL connections, which now have a newParams() method to create a parameter object, and an addParam(params,value,name=None) method to add parameters to the params object (created via newParams()) and return the string that should be used to reference the parameter.

    This lets you write SQL generation code with embedded parameters using "bind variables". For example, you could do something like this, if db is a SQL connection object:

            params = db.newParams()
            sql = 'SELECT * FROM foobar WHERE baz='+db.addParam(params, 42)
            rows = db(sql, params)

  • The peak script is now an .exe on Windows, using setuptools' "entry point" system.

  • PEAK no longer bundles any software that can be obtained automatically from PyPI. Running PEAK's setup script will attempt to download and install the needed packages. (Note that development snapshots of PEAK may require development snapshots of related packages.)

  • Added a series of new QueryDM and EntityDM convenience features. See Making Data Managers easier to use for a complete list and explanatory documentation.

  • Changed running.lookupCommand() to use the command's getCommandParent() method, so that commands using the --config option will utilize the specified configuration(s) to lookup subcommands.

  • Added a -c/--config option to PEAK bootstrap commands to load an .ini configuration file in a new service area before executing any subcommands.

    This allows you to do things like:

            peak launch -c bulletins ref:sitemap@sitemap.xml

    which loads the bulletins configuration file before launching the sitemap. Note that if you are subclassing commands.Bootstrap you can suppress this option using options.reject_inheritance("-c","--config") in the body of your subclass' class definition. You may wish to do this if your application's subcommands must run in the same service area as the parent command. (E.g. if the parent command expects the subcommand to partake in a transaction controlled by the parent command.)

  • Added a value property to model.Enumeration, so that you can access an enumeration instance's value (i.e., the value it hashes and compares equal to)

  • Added a binding.hasParent(component,parent) API function, which is specially optimized for use with generic functions, so that you can define generic function methods that apply only within some part of a component hierarchy.

  • PEAK no longer supports Python 2.2; Python 2.3.4 or better is required.

  • The kjbuckets extension module is no longer built and installed by default; you must explicitly enable it with a --with-kjbuckets flag passed to Please port your code as soon as practical, this option will go away soon.

  • Use of the included kjbuckets module is now DEPRECATED, due to increasing bitrot. Aaron Watters originally wrote this extension for Python 1.2, and it has not been well-maintained for newer versions of the Python/C API. Instead of kjSet objects, use the Python 2.3 Set type, and instead of the kjGraph type, use the new Graph type in peak.util.Graph. Some porting effort may be required, as these types are not precisely the same in signature as the originals.

  • The _setNS() method of the peak.util.SOX.ISOXNode_NS interface has changed signature, due to a lack of use of the second argument in the code base, and its dependency on kjbuckets.

  • The old implementation has been removed, and replaced with a simpler, more flexible implementation based on generic functions (using less than half the code and seven fewer interfaces). Complete documentation and API tests for the new implementation can be found in rules.txt in the package directory.

    Also, the new implemetation does not require redundant security.allow(security.Anybody) declarations just because you've declared other permissions for a class, so these declarations have been removed from ``peak.web``. They don't do any harm, however, so you can leave them in your own code as long as you change them to use binding.metadata() instead of the deprecated security.allow().

  • security.allow() is now DEPRECATED; please use binding.metadata() instead. (There is no change to the calling signature, but binding.metadata accepts any metadata, not just permissions.)

  • Added peak.running.options, a new option-parsing framework that extends optparse to support the PEAK commands framework. Command instances can now refer to self.parsed_args to find their non-option arguments, and to trigger setting of their attributes (or calling of methods) based on their raw arguments from self.argv. See options.txt in the peak.running package directory for a complete tutorial.

  • There is now a binding.initAttrs() function that can be used to initialize an object's attributes from e.g. constructor keyword arguments, similar to how binding.Component and binding.Attribute constructors work.

  • Security permissions can now be declared as attribute metadata.

    That is, instead of doing declarations like this:

            class Foo:
                bar = binding.Require("Something", permissionNeeded=SomePerm)
            class AnElement(model.Element):
                class someFeature(model.Attribute):
                    permissionNeeded = SomePerm

    you can (and should) now do them like this:

            class Foo:
                bar = binding.Require("Something", [SomePerm])
            class AnElement(model.Element):
                class someFeature(model.Attribute):
                    metadata = <a href="#SomePerm">[SomePerm]</a>

    or this:

            class Foo:
                binding.metadata(bar = [SomePerm])
            class AnElement(model.Element):
                binding.metadata(someFeature = [SomePerm])
                class someFeature(model.Attribute):
                    # ...

    It isn't necessary to enclose metadata in brackets, but it helps to emphasize its annotational nature. Also note that e.g. web.bindResource() needs metadata to be a keyword argument.

  • The permissionNeeded attribute of model.Feature and binding.Attribute objects is now DEPRECATED. See examples above for how to upgrade, and please switch to using metadata as soon as practical. In addition the security.IGuardedDescriptor interface has been removed, because it was only used in connection with the permissionNeeded attribute mechanism.

  • Added a new "attribute metadata" mini-framework to peak.binding. This framework makes it possible to declare arbitrary metadata about attributes, using either a class advisor (binding.metadata(), similar in form and function to the existing security.allow()) or using a metadata attribute of attribute bindings (which is the second positional parameter in all the standard bindings like Make, Obtain, etc.). Over time, existing metadata mechanisms will be refactored to use this new mini-framework, instead of the various integrated ad-hoc mechanisms that exist now (like the permissionNeeded attribute). For more information on how the new metadata hooks work, including doctest examples, see the attributes.txt file in the peak.binding package, under the heading "Attribute Metadata".

  • Added a new function, binding.activateClass(), that can be used to activate any bindings in the class. This can now be used in place of subclassing a PEAK base class or using a PEAK metaclass. In future, this will be integrated into PEAK attribute descriptors such that defining a descriptor within a class' body is sufficient to cause this function to be invoked.

  • binding.IBindingNode was REMOVED, consolidated into binding.IComponent, as its various individual methods have been replaced with generic functions in the existing binding API. For example, binding.getParentComponent(x) should be used in preference to x.getParentComponent() unless it is a requirement that x implement the full binding.IComponent interface. This makes it easier to define what binding.getParentComponent() and binding.getComponentName() will mean for non-component types, as you do not have to define an adapter class with all of the IBindingNode methods. Also, this makes PEAK itself cleaner, as we often weren't bothering to properly implement the full IBindingNode interface anyway.

    In addition, binding.suggestParentComponent() is now also a generic function, dispatching on the target (i.e. child) object.

  • naming.IReferenceable was REMOVED, as it is not in use anywhere in PEAK. This will be replaced with a generic function when we do actually need this functionality.

  • There is a new config.getStreamFactory generic function, to make it easy to accept URLs, filenames, or naming.IStreamFactory objects as the source of a "file".

    Its typical usage is just:

           factory = config.getStreamFactory(self,source)
           stream ='t')  # open for reading in text mode

    where source is a string or a naming.IStreamFactory, and self is a component to be used as lookup context. The returned factory is a naming.IStreamFactory that can then be '.open()'-ed for reading, or used in other ways as needed.

    If you have special objects that you'd like to be able to treat as stream sources, you can register them by defining an extension, e.g.:

        def getStreamFactory(context,source):
            """Return a naming.IStreamFactory for 'source' (a 'MyType' instance)"""

    Wherever practical, as we encounter them, we'll be changing PEAK API's that take filenames to also accept stream sources.

  • Added an optional base argument to naming.parseURL(), to allow parsing URLs relative to a base URL. For a URL scheme to support this, it must implement the new naming.IBaseURL interface. See the peak.naming.factories.openable module for example implementations.

  • Added a data: URL scheme, implementing RFC 2397 (although it's not as strict in its parsing of the content type and parameters as the RFC calls for). This is a semi-convenient way to provide configuration data in-line, since a data: URL can be a config.getStreamFactory() source.

  • Added config.processXML(), a function that provides a high-level, configuration-driven interface to peak.util.SOX.NegotiatingParser. This simple front-end lets you supply as little as a configuration context and a stream source, to do XML processing of arbitrary complexity, controlled by the configuration of the context.

  • Added config.XMLKey(), an IConfigKey type that can be used to register configuration values for XML attribute and element names under specified XML namespace URI's. Also, there are now [XML Attributes for nsuri] and [XML Elements for nsuri] section types available for use in .ini files. (Replace nsuri with the appropriate XML namespace URI, or use * for a wildcard.)

  • web.IResource is gone, replaced by web.IPlace. The notion of a place is broader than the notion of a resource, and we will soon need to have other "location" objects that implement IPlace.

  • In order to support obtaining the line and column locations of problems in XML files, we are now using Python 2.4's version of the pyexpat module, built as peak.util.pyexpat.

  • There's a new class, config.IniLoader, that can be used to lazily load .ini files as configuration. IniLoader instances have an iniFiles attribute that lists the configuration sources (filenames/URLs/factories) to be used, and automatically load the .ini files as soon as you try to get any configuration data for them. Previously, similar functionality was only available via config.makeRoot().

    Also, there's now an ini reference type that instantiates an IniLoader for one or more addresses. You can use it like this:

         [Named Services]
         some.example = naming.Reference('ini',
             ['pkgfile:peak/peak.ini', '/etc/something.ini']
         another.example = naming.LinkRef(

    The two examples above will each load the same pair of specified .ini files. You can also directly instantiate an IniLoader, as in:

         cfg = config.IniLoader(self, iniFiles=['pkgfile:peak/peak.ini'])

    Attempting to look up any configuration properties via the cfg object will cause it to load the specified .ini file.

  • config.fileNearModule() is DEPRECATED, in favor of config.packageFile(). The latter returns a naming.IStreamFactory, which is more suitable for working with e.g. module data files compressed in a zipfile. Uses of fileNearModule() that were being passed to config.loadConfigFile() can be safely changed to config.packageFile() without needing any other code changes, but if you were directly using fileNearModule() as a filename, you will need to rewrite appropriately.

  • config.loadConfigFile() and config.loadConfigFiles() now accept URLs, naming.IStreamFactory objects, and other config.getStreamFactory() targets as well as filenames. This was primarily added to support use of config.packageFile() or pkgfile: URLs, in place of using config.fileNearModule().

  • The naming.IStreamFactory interface now has an address attribute, which is the string form of the canonical URL of the target stream. This was added to make it easier to e.g. report errors in a stream that's being parsed, since the parser only needs the factory in order to report the location of an error. (Note: if you implement naming.IStreamFactory, be sure to add this attribute to your implementations.)

  • The peak.util.WSGIServer module has been moved to the wsgiref.simple_server module. The wsgiref reference library for WSGI (aka PEP 333) is now distributed with PEAK.

  • Added a WSGI command to the peak script, to allow you to run "foreign" (i.e. non-PEAK) PEP 333 applications in PEAK's various servers and launchers. Basically, by prefixing WSGI before the import specifier, you can now run such foreign apps.

    For example:

           peak launch WSGI import:some_app.application

    will run some_app.application in the local web browser, and:

           peak CGI WSGI import:some_app.application

    will run it under the CGI/FastCGI runner. Similarly, you can use this in the "Command" spec for the "peak supervise" pre-forking FastCGI supervisor subsystem.

  • There is a new running.IWSGIApplication interface, for PEP 333-compliant "application" objects, and all of PEAK's provided applications now implement it instead of running.IRerunnableCGI. If you write your apps to the newer interface, they'll be portable to any PEP 333-compliant web server, not just the PEAK CGI, FastCGI, and "supervisor" containers. There is a simple adapter that allows IWSGIApplication objects to run in the CGI-based containers, but not the other way around, so using IRerunnableCGI directly now limits your portability. (For example, the "peak launch" and "peak serve" commands will soon require IWSGIApplication, and will not support IRerunnableCGI any more.)

    Of course, if you use the peak.web framework, you don't need to worry about any of this; your apps will automatically be wrapped as IWSGIApplication, and run in any PEAK server or gateway.

  • Most peak.web interfaces have changed significantly. If you implemented anything based on the older interfaces, and it still works, it's sheer bloody luck. In particular, note that every method in web.IWebTraversable now has different inputs and/or outputs than before. Please read the new interface docs and update your code! The changed interfaces offer much more flexibility and functionality than before, but they will require you to update your code.

  • web.ContainerAsTraversable has been removed. It was redundant, since the new default traversal mechanism used by Traversable and Decorator now handles getitem, getattr, and views.

  • Added Zope 3-like "namespaces" to peak.web. Path segments in a URL may be prefixed with "++some_id++" in order to invoke a corresponding namespace handler registered under "peak.web.namespaces.some_id". Namespace handlers must implement web.INamespaceHandler, and they are supplied with the original path segment as well as the separated namespace and name. Also, as in Zope 3, "@@foo" is a shortcut for "++view++foo". Builtin namespaces at this time include view, item, attr, skin, and resources. skin treats the rest of its path segment as a skin name, and sets the current skin, while resources begins traversal to resources found in the current skin. The other namespaces are as described at:

    Resources and traversal in peak.web

  • Fixed several bugs, as reported by Vladimir Iliev, Yaroslav Samchuk, and Alexander Smishlajev:

    • events.AnyOf could hold multiple references to a single event source, and nesting AnyOf() calls could leak references to the nested events.

    • events.subscribe() had a potential race condition wherein a callback could be invoked after its weak reference was garbage collected, leading to bizarre error messages about self being None.

    • select() could be called on select event objects even if there were no current subscribers to the event, potentially leading to calling select() on a closed socket.

    • Non-default signal handlers were remaining installed even when there were no current subscribers to the applicable event, as long as a reference to the event object existed.

    As a result of these changes, certain I/O event types (esp. signals and stream readable/writeable events) are now longer-lived. For example, signal event objects are now immortal, and the read/write event for a particular fileno() will be reused for as long as its supplying Selector or EventLoop instance exists. (Previously, weak references were used so that these objects would be recycled when not in use.)

  • Added config.registeredProtocol() API, that supports defining named and local protocols. This allows easy emulation of Zope 3's "named" and "local" adapters and views.

  • binding.Component objects no longer support instance configuration at runtime (i.e., they no longer implement config.IConfigurable). If you need a component to be configurable at runtime, you must now derive from (or mix in) binding.Configurable instead. If you get errors about a missing registerProvider attribute, or about being unable to adapt to IConfigurable, try changing your base class from binding.Component to binding.Configurable, or add it as a mixin if you're deriving from a class that uses binding.Component as its base.

  • binding.IComponent no longer derives from config.IConfigurable or config.IConfigMap, only config.IConfigSource. This means that IComponent no longer guarantees or requires the presence of the registerProvider() method: now only config.IConfigurable does that.

  • The config.IConfigMap interface is now DEPRECATED. Use config.IConfigurable instead. The _configKeysMatching() method of IConfigMap was moved to config.IConfigSource, so if you've implemented a custom IConfigSource, be sure to add this method.

  • web.ISkinService and web.ILayerService were consolidated into web.IInteractionPolicy, because the need to have configurable implementations of these services is negligible. That is, the corresponding property namespaces (peak.web.skins and peak.web.layers) are more than adequate as registries.

  • Removed peak.running.timers and peak.util.dispatch. Neither was in active use, and both are being replaced by the new generic functions package in PyProtocols.

  • The config.iterParents API is now moved to binding.iterParents, and all binding functions that walk the component hierarchy use it. It has also been changed to avoid infinite loops in the case of a pathological component structure.

  • The persistence package has been moved to peak.persistence to avoid conflicts with ZODB3 and the latest version of Zope 3. It will eventually be phased out, but for now this move is the simplest way to get it out of the way.

  • The peak.util.SOX module now uses only one parser, based directly on expat, instead of using SAX. The new parser expects a new node interface, IXMLBuilder, but adapters from the previous interfaces (ISOXNode and ISOXNode_NS) are supplied for backward compatibility. All of PEAK's direct XML handling (currently just and peak.web.templates) have been refactored to use the new interface. Some parsing classes (such as ObjectMakingHandler, NSHandler, and DOMletParser) are no longer available.

  • peak.web no longer uses Zope X3 for HTTP publishing support; it has been refactored to use a simpler, more uniform architecture See also more on the architecture and subsequent posts in that thread.

    As a consequence, various features have been removed from peak.web, for possible return at a future date. Here is a rough outline of the changes made so far:

    • The pageProtocol, pathProtocol, and errorProtocol machinery are gone. They will be replaced in the future with an explicit "controller" wrapping mechanism to allow application-specific renderings of the same underlying components.

    • The Zope request and response objects are gone, along with all of their special handling for cookies, character sets, form variables, automatically marshalling parameters to functions, etc. These items of functionality will be gradually replaced by functions in peak.web.api.

      As a result of this, arbitrary functions and methods can no longer be used as web pages; instead, functions and methods to be published must use the same inputs and outputs as the IHTTPHandler.handle_http() method.

    • The IWebPage, IWebInteraction, ITraversalContext, Traversal, TraversalContext, and Interaction interfaces and classes no longer exist, as they are unneeded in the new architecture. Instead of having a central IWebInteraction that's referenced by numerous ITraversalContext objects, the new approach uses an environ mapping for most functions. For access control, a security.IInteraction is now used, whose function is limited to security checks. Most functions previously performed by IWebInteraction have moved to IInteractionPolicy or to peak.web.api functions operating on environ mappings.

    • Web exceptions can define a levelName attribute that determines the severity level with which the exception will be logged. This allows one to e.g. avoid logging tracebacks for NotFound errors.

    • Various interface calling signatures have changed slightly. For example, IAuthService.getUser() now accepts an environ mapping instead of an interaction. IInteractionPolicy.newInteraction() now takes keyword arguments, but not a request. The IWebTraversable interface no longer has a getObject() method, and the IWebException.handleException() method signature has changed as well. Finally, all methods that previously accepted ITraversalContext (such as IDOMletState.renderFor()) now expect environ mappings.

    • web.TestInteraction was replaced with web.TestPolicy, and web.Interaction was removed, since IWebInteraction is no longer part of the architecture.

  • The log() method of PEAK loggers (logs.ILogger) now accepts a level name or a number, for convenient invocation.

  • SQL transaction semantics have changed. Now, issuing an SQL statement always causes the connection to join the active PEAK transaction, even if you request that the SQL be issued "outside" a transaction. Such SQL will be issued outside of the database transaction, but not outside of the PEAK transaction. This simplifies the overall processing model for dealing with "untransacted" SQL such as Sybase DDL or read-only Oracle transactions. (In particular, the requirement that triggered this change was to allow Oracle read-only transactions to be released at the end of the current PEAK transaction.) Also, got rid of the now-meaningless begin command in n2.

  • The events.IEventSource interface now returns a canceller function from the addCallback() method, allowing you to cancel a previously-scheduled callback. This fixes a memory leak and performance problem with events.AnyOf(), which previously could accumulate unneeded callbacks on the sources it was monitoring. Note that if you have developed any custom event sources with addCallback() methods, you must make sure that they return a canceller from now on.

  • Added ref:factory@addr1||addr2 URL scheme that maps to a corresponding naming.Reference("factory",["addr1","addr2"]). factory can be either a dotted import string referencing a naming.IObjectFactory, or you can define a factory in the peak.naming.factories property space.

  • Added a zconfig.schema factory, so that ref:zconfig.schema@streamURL will load a schema loader. Schema loaders are themselves object factories, so you can do something like:

         [Named Services]
         peak.naming.factories.myschema = \
       in order to make URLs like 'ref:myschema@filename' work.  Note, by the way,
       that the above could also read::
         [Named Services]
         peak.naming.factories.myschema = \
       which runs somewhat faster at lookup time.  Similarly, one can also use
       'naming.Reference("myschema",["somefile"])' in place of a
       'naming.LinkRef("ref:myschema@filename")'.  As well as being faster, for
       some use cases it's easier to 'Reference' directly than to glue together
       a 'ref:' URL string.

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