Importing Schema from CSV Files
===============================

We allow users to spell schema definitions via CSV text files, where the
columns are 'Name', 'Type', 'Default'. E.g.::

>>> _SCHEMA = '''\
... foo,TextLine,Foo
... bar,Int,42
... spam,Float,3.1415926
... baz,Text,"Multi-line text is
... possible in CSV."
... qux,Choice,two,one,two,three
... quux,ChoiceSet,"two,three",one,two,three
... frobnatz,Bool,True'''

When we construct a schema from the CSV, we get a Zope3 interface (just
as though we had typed the equivalent Python faux-class syntax)::

>>> from zope.interface.interface import InterfaceClass
>>> from zope.schema import Bool
>>> from zope.schema import Choice
>>> from zope.schema import Float
>>> from zope.schema import Int
>>> from zope.schema import Text
>>> from zope.schema import TextLine
>>> from userschema.schema import ChoiceSet
>>> from userschema.schema import fromCSV

We must pass the name of the generated schema to 'fromCSV', along with
the CSV text (or a file-like object)::

>>> a_schema = fromCSV(_SCHEMA, 'a_schema')
>>> type(a_schema) is InterfaceClass
True
>>> print a_schema.__name__
a_schema

The '__module__' attribute of the generated interface defaults to
'userschema'::

>>> print a_schema.__module__
userschema

We can override that by passing 'module_name'::

>>> a_schema = fromCSV(_SCHEMA, 'a_schema', module_name='somemodule')
>>> print a_schema.__module__
somemodule

The attributes of the generated schema correspond to the rows in
the CSV::

>>> names = list(a_schema.names())
>>> names.sort()
>>> print names
['bar', 'baz', 'foo', 'frobnatz', 'quux', 'qux', 'spam']

We create the fields we would expect from the types defined in the CSV.
The 'foo' field is a TextLine::

>>> field = a_schema.getDescriptionFor('foo')
>>> isinstance(field, TextLine)
True
>>> print field.default
Foo

The 'bar' field is an Int::

>>> field = a_schema.getDescriptionFor('bar')
>>> isinstance(field, Int)
True
>>> print field.default
42

The 'spam' field is an Float::

>>> field = a_schema.getDescriptionFor('spam')
>>> isinstance(field, Float)
True
>>> print field.default
3.1415926

The 'baz' field is a Text, with multi-line default::

>>> field = a_schema.getDescriptionFor('baz')
>>> isinstance(field, Text)
True
>>> print field.default
Multi-line text is
possible in CSV.


The 'qux' field is a Choice, with the vocabulary defined in the
extra columns::

>>> field = a_schema.getDescriptionFor('qux')
>>> isinstance(field, Choice)
True
>>> print field.default
two
>>> print [str(x.value) for x in field.vocabulary]
['one', 'two', 'three']

The 'quux' field is a ChoiceSet, with the vocabulary defined in the
extra columns::

>>> field = a_schema.getDescriptionFor('quux')
>>> isinstance(field, ChoiceSet)
True
>>> print field.default
Set([u'two', u'three'])
>>> print [str(x.value) for x in field.vocabulary]
['one', 'two', 'three']

The 'frobnatz' field is a TextLine::

>>> field = a_schema.getDescriptionFor('frobnatz')
>>> isinstance(field, Bool)
True
>>> print field.default
True

CVS: $Id: csv-schema.txt,v 1.2 2007-01-31 16:58:07 tseaver Exp $