Module typedstruct

source code

Typed Data Structures

This module provides helpers for creating typed data structures.

Basic Usage

In order to create a new data structure, you inherit from Struct and define the members like so (the booleans are explained later):

   class MyStruct(typedstruct.Struct):
       __slots__ = typedstruct.members(locals(), {
           'name1': None,
           # ... and/or ...
           'name2': <type>,
           # ... and/or ...
           'name3': (<type>, <param>),
       })

If there are no fixed types at all (always None, you can still benefit from the features of the Struct class and further write it a bit simpler:

   class MyStruct(typedstruct.Struct):
       __slots__ = typedstruct.members(locals(), (
           'name1', 'name2', ...
       ))

Well, the main reason for using the Struct class is to get some level of type safety and automatic conversion without a complex written definition of property for each and every member (it uses some property like descriptors internally, however). This encapsulates a lot of ugly logic and error handling (more or less) into a single piece of code and makes the member definitions much easier to read and maintain. For example, you can create a struct member of type regex. Now you assign a string to this member and it is automatically compiled to a regex, which you get, if you retrieve the value later. As you'll see, the regex type needs to be defined as a class which should be inherited from the MemberDescriptor class and assigned to the regex type name via a type mapping dict:

   class RegexMember(typedstruct.MemberDescriptor):
       def transform(self, value, arg):
           import re
           return re.compile(value)
   # ...
   typemap = {'regex': RegexMember}
   # ...
   class MyStruct(typedstruct.Struct):
       __slots__ = typedstruct.members(locals(), {
           'checker': 'regex',
       }, typemap = typemap)
   # ...
   store = MyStruct()
   store.checker = r'[a-zA-Z]$'
   # ...
   if store.checker.match(stringtocheck):
       # do something

Constraints

Member names must be valid python identifiers. Further all names starting and ending with underscores are reserved for Struct's or python's own purposes.