Reference

The dum module define a set of function to generate python objects from the projection of data structured in xml, json or csv.

Node protocol

The Node protocol must be defined by the classes that host the result of the data projection.

class Node

A class complying to the Node protocol must accept an empty constructor and define :

class dum

This static class is used as a namespace to store the projection fields.

The dum class can also define the following attributes:

__namespaces__

a mapping from namespace prefix to full name

__default_namespaces__

a string with the full name of the element hierarchy

dum_projection()

This optional method is called when the closing tag is parsed. Define it to return an alternative object (masquerade) or to perform some post parsing process. In the second case the method should return self.

Each projection field is a dum class member with the form :

target = converter[, source]

• target is the name of the python’s object attribute
• converter is the function used to convert input data to python value. It may be replaced by a default value which will be used as prototype. Conveter may be but inside a list to denote that value must me collected as list.
• source is the localization of the data in the input document. It is a string which must conform to a subset of xPath. This source segment is optional, by default dum will look for a child with the same name than the target.

Module content

dum.DUM_NONE

returned by converter functions when a value should be ignored

dum.group(name1=type1[, name2=type2...])

All child elements corresponding to name1,name2... should be collected in the same list after being interpreted by type1, type2... converter. You can give a dictionary as first argument if some child name are not valid Python identifiers. The group fields are only used for Xml parsing.

@dum.converter

@dum.converter(source, default)

Use these decorator when you need to define a function to convert values. The form without argument is optional : you can use raw function as well.

Parameters:

• source – xPath string for locating value in input data
• default – value to use if nothing is found in input data

@dum.lister

@dum.lister(source)

When you need converter to be applied on a collection of values

Parameters:source – xPath string for locating value in input data

dum.xml(Node, fd)

Parse the xml file stored in the file descriptor fd, an project it’s root element into the Node class.

Parameters:

• Node – class conforming to the Node protocol
• fd – file descriptor opened for reading at the start of the xml data.

Returns:

Node instance initialized from xml root element.

dum.xmls(Node, text)

Parse the xml present in text string.

Parameters:

• Node – class conforming to the Node protocol
• text – string containing the xml data.

Returns:

Node instance initialized from xml root element.

dum.json(Node, object)

Project object root element into the Node class; object may come from json.load function.

Parameters:

• Node – class conforming to the Node protocol
• object – dictionary corresponding of the root of json data.

Returns:

Node instance initialized from object.

dum.csv(Node, iterator[, header])

Parse and project tabulated data from iterator into the Node class. The iterator object may come from csv.reader

Parameters:

• Node – class conforming to the Node protocol
• iterator – iterator yielding fixed length rows in the form of list of strings
• header – column name are used to interpret dum field source. If the header list it present it will be used for column names, else the first row of the iterator will be used.

Returns:

a generator of Node instances initialized from input rows values.