API and Code¶
Below is the API documention for the the Stetl Python code.
Main Entry Points¶
There are several entry points through which Stetl can be called. The most common is to use the commandline script bin/stetl. This command should be available after doing an install.
In some contexts like integrations you may want to call Stetl via Python. The entries are then.
-
stetl.main.
main
()[source]¶ The main function, to be called from commandline, like python src/main.py -c etl.cfg.
- Args:
-c --config <config_file> the Stetl config file. -s –section <section_name> the section in the Stetl config (ini) file to execute (default is [etl]). -a –args <arglist> substitutable args for symbolic, {arg}, values in Stetl config file, in format “arg1=foo arg2=bar” etc. -d –doc <class> Get component documentation like its configuration parameters, e.g. stetl –doc stetl.inputs.fileinput.FileInput -h –help get help info
Core Framework¶
The core framework is directly under the directory src/stetl. Below are the main seven classes. Their interrelation is as follows:
One or more stetl.chain.Chain
objects are built from
a Stetl ETL configuration via the stetl.factory.Factory
class.
A stetl.chain.Chain
consists of a set of connected stetl.component.Component
objects.
A stetl.component.Component
is either an stetl.input.Input
, an stetl.output.Output
or a stetl.filter.Filter
. Data and status flows as stetl.packet.Packet
objects
from an stetl.input.Input
via zero or more stetl.filter.Filter
objects to a final stetl.output.Output
.
As a trivial example: an stetl.input.Input
could be an XML file, a stetl.filter.Filter
could represent
an XSLT file and an stetl.output.Output
a PostGIS database. This is effected by specialized classes in
the subpackages inputs, filters, and outputs.
-
class
stetl.factory.
Factory
[source]¶ Object and class Factory (Pattern). Based on: http://stackoverflow.com/questions/2226330/instantiate-a-python-class-from-a-name
-
class
stetl.component.
Component
(configdict, section, consumes='none', produces='none')[source]¶ Abstract Base class for all Input, Filter and Output Components.
-
input_format
()[source]¶ CONFIG
- The specific input format if the consumes parameter is a list or the format to be converted to the output_format. Required: False Default: None
-
-
class
stetl.component.
Config
(ptype=<type 'str'>, default=None, required=False)[source]¶ Decorator class to tie config values from the .ini file to object instance property values. Somewhat like the Python standard @property but with the possibility to define default values, typing and making properties required.
Each property is defined by @Config(type, default, required). Basic idea comes from: https://wiki.python.org/moin/PythonDecoratorLibrary#Cached_Properties
-
class
stetl.chain.
Chain
(chain_str, config_dict)[source]¶ Holder for single invokable pipeline of components A Chain is basically a singly linked list of Components Each Component executes a part of the total ETL. Data along the Chain is passed within a Packet object. The compatibility of input and output for linked Components is checked when adding a Component to the Chain.
-
class
stetl.packet.
Packet
(data=None)[source]¶ Represents units of (any) data and status passed along Chain of Components.
-
class
stetl.input.
Input
(configdict, section, produces)[source]¶ Bases:
stetl.component.Component
Abstract Base class for all Input Components.
-
class
stetl.output.
Output
(configdict, section, consumes)[source]¶ Bases:
stetl.component.Component
Abstract Base class for all Output Components.
-
class
stetl.filter.
Filter
(configdict, section, consumes, produces)[source]¶ Bases:
stetl.component.Component
Maps input to output. Abstract base class for specific Filters.
Components: Inputs¶
-
class
stetl.inputs.dbinput.
DbInput
(configdict, section, produces)[source]¶ Bases:
stetl.input.Input
Input from any database (abstract base class).
-
class
stetl.inputs.dbinput.
PostgresDbInput
(configdict, section)[source]¶ Bases:
stetl.inputs.dbinput.SqlDbInput
Input by querying records from a Postgres database. Input is a query, like SELECT * from mytable. Output is zero or more records as record array (array of dict) or single record (dict).
produces=FORMAT.record_array (default) or FORMAT.record
-
class
stetl.inputs.dbinput.
SqlDbInput
(configdict, section, produces)[source]¶ Bases:
stetl.inputs.dbinput.DbInput
Input using a query from any SQL-based RDBMS (abstract base class).
-
column_names
()[source]¶ CONFIG
- Column names to populate records with. If empty taken from table metadata.
-
-
class
stetl.inputs.dbinput.
SqliteDbInput
(configdict, section)[source]¶ Bases:
stetl.inputs.dbinput.SqlDbInput
Input by querying records from a SQLite database. Input is a query, like SELECT * from mytable. Output is zero or more records as record array (array of dict) or single record (dict).
produces=FORMAT.record_array (default) or FORMAT.record
-
class
stetl.inputs.fileinput.
ApacheLogFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Parses Apache log files. Lines are converted into records based on the log format. Log format should follow Apache Log Format. See ApacheLogParser for details.
produces=FORMAT.record
-
key_map
()[source]¶ CONFIG
- Map of cryptic %-field names to readable keys in record.Type: dictionary
Required: False
Default: {‘%l’: ‘logname’, ‘%>s’: ‘status’, ‘%D’: ‘deltat’, ‘%{User-agent}i’: ‘agent’, ‘%b’: ‘bytes’, ‘%{Referer}i’: ‘referer’, ‘%u’: ‘user’, ‘%t’: ‘time’, “’%h”: ‘host’, ‘%r’: ‘request’}
-
-
class
stetl.inputs.fileinput.
CsvFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Parse CSV file into stream of records (dict structures) or a one-time record array. NB raw version: CSV needs to have first line with fieldnames.
produces=FORMAT.record or FORMAT.record_array
-
class
stetl.inputs.fileinput.
FileInput
(configdict, section, produces)[source]¶ Bases:
stetl.input.Input
Abstract base class for specific FileInputs, use derived classes.
-
depth_search
()[source]¶ CONFIG
- Should we recurse into sub-directories to find files?Required: False
Default: False
-
file_path
()[source]¶ CONFIG
- Path to file or files or URLs: can be a dir or files or URLs or even multiple, comma separated. For URLs only JSON is supported now.Required: True
Default: None
-
-
class
stetl.inputs.fileinput.
JsonFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Parse JSON file from file system or URL into hierarchical data struct. The struct format may also be a GeoJSON structure. In that case the output_format needs to be explicitly set to geojson_collection in the component config.
produces=FORMAT.struct or FORMAT.geojson_collection
-
class
stetl.inputs.fileinput.
LineStreamerFileInput
(configdict, section, produces='line_stream')[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Reads text-files, producing a stream of lines, one line per Packet. NB assumed is that lines in the file have newlines !!
-
class
stetl.inputs.fileinput.
StringFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Reads and produces file as String.
produces=FORMAT.string
-
class
stetl.inputs.fileinput.
XmlElementStreamerFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Extracts XML elements from a file, outputs each feature element in Packet. Parsing is streaming (no internal DOM buildup) so any file size can be handled. Use this class for your big GML files!
produces=FORMAT.etree_element
CONFIG
- Comma-separated string of XML (feature) element tag names of the elements that should be extracted and added to the output element stream.Required: True
Default: None
-
class
stetl.inputs.fileinput.
XmlFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Parses XML files into etree docs (do not use for large files!).
produces=FORMAT.etree_doc
-
class
stetl.inputs.fileinput.
XmlLineStreamerFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.LineStreamerFileInput
DEPRECATED Streams lines from an XML file(s) NB assumed is that lines in the file have newlines !! DEPRECATED better is to use XmlElementStreamerFileInput for GML features.
produces=FORMAT.xml_line_stream
-
class
stetl.inputs.fileinput.
ZipFileInput
(configdict, section)[source]¶ Bases:
stetl.inputs.fileinput.FileInput
Parse ZIP file from file system or URL into a stream of records containing zipfile-path and file names.
produces=FORMAT.record
-
class
stetl.inputs.httpinput.
ApacheDirInput
(configdict, section, produces='record')[source]¶ Bases:
stetl.inputs.httpinput.HttpInput
Read file data from an Apache directory “index” HTML page. Uses http://stackoverflow.com/questions/686147/url-tree-walker-in-python produces=FORMAT.record. Each record contains file_name and file_data (other meta data like date time is too fragile over different Apache servers).
-
class
stetl.inputs.httpinput.
HttpInput
(configdict, section, produces='any')[source]¶ Bases:
stetl.input.Input
Fetch data from remote services like WFS via HTTP protocol. Base class: subclasses will do datatype-specific formatting of the returned data.
produces=FORMAT.any
-
format_data
(data)[source]¶ Format response data, override in subclasses, defaults to returning original data. :param packet: :return:
-
parameters
()[source]¶ CONFIG
- Flat JSON-like struct of the parameters to be appended to the url.Example: (parameters require quotes):
url = http://geodata.nationaalgeoregister.nl/natura2000/wfs parameters = { service : WFS, version : 1.1.0, request : GetFeature, srsName : EPSG:28992, outputFormat : text/xml; subtype=gml/2.1.2, typename : natura2000 }
Required: False
Default: None
-
-
class
stetl.inputs.ogrinput.
OgrInput
(configdict, section)[source]¶ Bases:
stetl.input.Input
Direct GDAL OGR input via Python OGR wrapper. Via the Python API http://gdal.org/python an OGR data source is accessed and from each layer the Features are read. Each Layer corresponds to a “doc”, so for multi-layer sources the ‘end-of-doc’ flag is set after a Layer has been read.
This input can read almost any geospatial dataformat. One can use the features directly in a Stetl Filter or use a converter to e.g. convert to GeoJSON structures.
produces=FORMAT.ogr_feature or FORMAT.ogr_feature_array (all features)
-
data_source
()[source]¶ CONFIG
- String denoting the OGR datasource. Usually a path to a file like “path/rivers.shp” or connection string to PostgreSQL like “PG: host=localhost dbname=’rivers’ user=’postgres’”.Required: True
Default: None
-
source_format
()[source]¶ CONFIG
- Instructs GDAL to use driver by that name to open datasource. Not required for many standard formats that are self-describing like ESRI Shapefile.Examples: ‘PostgreSQL’, ‘GeoJSON’ etc
Required: False
Default: None
-
-
class
stetl.inputs.ogrinput.
OgrPostgisInput
(configdict, section)[source]¶ Bases:
stetl.input.Input
Input from PostGIS via ogr2ogr command. For now hardcoded to produce an ogr GML line stream. OgrInput may be a better alternative.
Alternatives: either stetl.input.PostgresqlInput or stetl.input.OgrInput.
produces=FORMAT.xml_line_stream
-
class
stetl.inputs.deegreeinput.
DeegreeBlobstoreInput
(configdict, section)[source]¶ Bases:
stetl.input.Input
Read features from deegree Blobstore DB into an etree doc.
produces=FORMAT.etree_doc
Components: Filters¶
-
class
stetl.filters.xsltfilter.
XsltFilter
(configdict, section)[source]¶ Bases:
stetl.filter.Filter
Invokes XSLT processor (via lxml) for given XSLT script on an etree doc.
consumes=FORMAT.etree_doc, produces=FORMAT.etree_doc
-
class
stetl.filters.xmlassembler.
XmlAssembler
(configdict, section)[source]¶ Bases:
stetl.filter.Filter
Split a stream of etree DOM XML elements (usually Features) into etree DOM docs. Consumes and buffers elements until max_elements reached, will then produce an etree doc.
consumes=FORMAT.etree_element, produces=FORMAT.etree_doc
-
class
stetl.filters.xmlvalidator.
XmlSchemaValidator
(configdict, section)[source]¶ Bases:
stetl.filter.Filter
Validates an etree doc and prints result to log.
consumes=FORMAT.etree_doc, produces=FORMAT.etree_doc
-
class
stetl.filters.stringfilter.
StringFilter
(configdict, section, consumes, produces)[source]¶ Bases:
stetl.filter.Filter
Base class for any string filtering
-
class
stetl.filters.stringfilter.
StringSubstitutionFilter
(configdict, section)[source]¶ Bases:
stetl.filters.stringfilter.StringFilter
String filtering using Python advanced String formatting. String should have substitutable values like {schema} {foo} format_args should be of the form format_args = schema:test foo:bar ...
consumes=FORMAT.string, produces=FORMAT.string
-
class
stetl.filters.templatingfilter.
Jinja2TemplatingFilter
(configdict, section)[source]¶ Bases:
stetl.filters.templatingfilter.TemplatingFilter
Implements Templating using Jinja2. Jinja2 http://jinja.pocoo.org, is a modern and designer-friendly templating language for Python modelled after Django’s templates. A ‘struct’ format as input provides a tree-like structure that could originate from a JSON file or REST service. This input struct provides all the variables to be inserted into the template. The template itself can be configured in this component as a Jinja2 string or -file. An optional ‘template_search_paths’ provides a list of directories from which templates can be fethced. Default is the current working directory. Via the optional ‘globals_path’ a JSON structure can be inserted into the Template environment. The variables in this globals struture are typically “boilerplate” constants like: id-prefixes, point of contacts etc.
consumes=FORMAT.struct, produces=FORMAT.string
-
add_env_filters
(jinja2_env)[source]¶ Register additional Filters on the template environment by updating the filters dict: Somehow min and max of list are not present so add them as well.
-
static
geojson2gml_filter
(value, source_crs=4326, target_crs=None, gml_id=None, gml_format='GML2', gml_longsrs='NO')[source]¶ Jinja2 custom Filter: generates any GML geometry from a GeoJSON geometry. By specifying a target_crs we can even reproject from the source CRS. The gml_format=GML2|GML3 determines the general GML form: e.g. pos/posList or coordinates. gml_longsrs=YES|NO determines the srsName format like EPSG:4326 or urn:ogc:def:crs:EPSG::4326 (long).
-
-
class
stetl.filters.templatingfilter.
StringTemplatingFilter
(configdict, section)[source]¶ Bases:
stetl.filters.templatingfilter.TemplatingFilter
Implements Templating using Python’s internal string.Template. A template string or file should be configured. The input record contains the actual values to be substituted in the template string as a record (key/value pairs). Output is a regular string.
consumes=FORMAT.record or FORMAT.record_array, produces=FORMAT.string
-
class
stetl.filters.templatingfilter.
TemplatingFilter
(configdict, section, consumes='any', produces='string')[source]¶ Bases:
stetl.filter.Filter
Abstract base class for specific template-based filters. See https://wiki.python.org/moin/Templating Subclasses implement a specific template language like Python string.Template, Mako, Genshi, Jinja2,
consumes=FORMAT.any, produces=FORMAT.string
-
class
stetl.filters.gmlfeatureextractor.
GmlFeatureExtractor
(configdict, section='gml_feature_extractor')[source]¶ Bases:
stetl.filter.Filter
Extract arrays of GML features etree elements from etree docs.
consumes=FORMAT.etree_doc, produces=FORMAT.etree_feature_array
-
class
stetl.filters.gmlsplitter.
GmlSplitter
(configdict, section='gml_splitter')[source]¶ Bases:
stetl.filter.Filter
Split a stream of text XML lines into documents DEPRECATED: use the more robust XmlElementStreamerFileInput+XmlAssembler instead!!! TODO phase out
consumes=FORMAT.xml_line_stream, produces=FORMAT.etree_doc
-
class
stetl.filters.formatconverter.
FormatConverter
(configdict, section)[source]¶ Bases:
stetl.filter.Filter
Converts (almost) any packet format (if converter available).
consumes=FORMAT.any, produces=FORMAT.any but actual formats are changed at initialization based on the input to output format to be converted via the input_format and output_format config parameters.
-
converter_args
()[source]¶ CONFIG
- Custom converter-specific arguments.Type: dictionary
Required: False
Default: None
-
static
etree_doc2geojson_collection
(packet, converter_args=None)[source]¶ Use converter_args to determine XML tag names for features and GeoJSON feature id. For example
- converter_args = {
- ‘root_tag’: ‘FeatureCollection’, ‘feature_tag’: ‘featureMember’, ‘feature_id_attr’: ‘fid’ }
Parameters: - packet –
- converter_args –
Returns:
-
Components: Outputs¶
-
class
stetl.outputs.fileoutput.
FileOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Pretty print input to file. Input may be an etree doc or any other stringify-able input.
consumes=FORMAT.any
-
class
stetl.outputs.fileoutput.
MultiFileOutput
(configdict, section)[source]¶ Bases:
stetl.outputs.fileoutput.FileOutput
Print to multiple files from subsequent packets like strings or etree docs.
consumes=FORMAT.any
-
class
stetl.outputs.standardoutput.
StandardOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Print any input to standard output.
consumes=FORMAT.any
-
class
stetl.outputs.standardoutput.
StandardXmlOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Pretty print XML from etree doc to standard output. OBSOLETE, can be done with StandardOutput
consumes=FORMAT.etree_doc
-
class
stetl.outputs.httpoutput.
HttpOutput
(configdict, section, consumes='any')[source]¶ Bases:
stetl.output.Output
Output via HTTP protocol, usually via POST.
consumes=FORMAT.etree_doc
-
class
stetl.outputs.ogroutput.
Ogr2OgrOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Output from GML etree doc to any OGR2OGR output using the GDAL/OGR ogr2ogr command
consumes=FORMAT.etree_doc
-
class
stetl.outputs.ogroutput.
OgrOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Direct GDAL OGR output via Python OGR wrapper. Via the Python API http://gdal.org/python OGR Features are written.
This output can write almost any geospatial, OGR-defined, dataformat.
consumes=FORMAT.ogr_feature or FORMAT.ogr_feature_array
-
append
()[source]¶ CONFIG
- Add to destination destination if it extists (ogr2ogr -append option).Type: boolean
Required: False
Default: False
-
dest_data_source
()[source]¶ CONFIG
- String denoting the OGR data destination. Usually a path to a file like “path/rivers.shp” or connection string to PostgreSQL like “PG: host=localhost dbname=’rivers’ user=’postgres’”.Required: True
Default: None
-
dest_format
()[source]¶ CONFIG
- Instructs GDAL to use driver by that name to open data destination. Not required for many standard formats that are self-describing like ESRI Shapefile.Examples: ‘PostgreSQL’, ‘GeoJSON’ etc
Required: False
Default: None
-
dest_options
()[source]¶ CONFIG
- Custom data destination-specific options. Used in gdal.SetConfigOption().Type: dictionary
Required: False
Default: None
-
layer_create_options
()[source]¶ CONFIG
- Options for newly created layer (-lco).Type: list
Required: True
Default: []
-
new_layer_name
()[source]¶ CONFIG
- Layer name for layer created in the destination source.Type: string
Required: True
-
overwrite
()[source]¶ CONFIG
- Overwrite destination if it extists (ogr2ogr -overwrite option).Type: boolean
Required: False
Default: False
-
-
class
stetl.outputs.dboutput.
DbOutput
(configdict, section, consumes)[source]¶ Bases:
stetl.output.Output
Output to any database (abstract base class).
-
class
stetl.outputs.dboutput.
PostgresDbOutput
(configdict, section)[source]¶ Bases:
stetl.outputs.dboutput.DbOutput
Output to PostgreSQL database. Input is an SQL string. Output by executing input SQL string.
consumes=FORMAT.string
-
class
stetl.outputs.dboutput.
PostgresInsertOutput
(configdict, section, consumes='record')[source]¶ Bases:
stetl.outputs.dboutput.PostgresDbOutput
Output by inserting single record into Postgres database. Input is a record (Python dic structure) or a Python list of dicts (records). Creates an INSERT for Postgres to insert each single record. When the “replace” parameter is True, any existing record keyed by “key” is attempted to be deleted first.
NB a constraint is that each record needs to contain all values as an INSERT query is built once for the columns in the first record.
consumes=FORMAT.record
-
class
stetl.outputs.wfsoutput.
WFSTOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Insert features via WFS-T (WFS Transaction) OGC protocol from an etree doc.
consumes=FORMAT.etree_doc
-
class
stetl.outputs.deegreeoutput.
DeegreeBlobstoreOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Insert features into deegree Blobstore from an etree doc.
consumes=FORMAT.etree_doc
-
class
stetl.outputs.deegreeoutput.
DeegreeFSLoaderOutput
(configdict, section)[source]¶ Bases:
stetl.output.Output
Insert features via deegree using deegree’s FSLoader tool from an etree doc.
consumes=FORMAT.etree_doc