Re-forecasts:  1 param, 1 date 

 #!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
    "class": "s2",
    "dataset": "s2s",
    "hdate": "1981-01-01",
    "date": "2014-01-01", 
    "expver": "prod",
    "levtype": "sfc",
    "origin": "ammc",
    "param": "tp",
    "step": "24/to/1488/by/24",
    "stream": "enfh",
    "target": "CHANGEME",
    "time": "00",
    "type": "cf",
})
  #!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
    "class": "s2",
    "dataset": "s2s",
    "hdate": "1981-01-01",
    "date": "2014-01-01", 
    "expver": "prod",
    "levtype": "sfc",
    "origin": "ammc",
    "param": "tp",
    "step": "24/to/1488/by/24",
    "stream": "enfh",
    "target": "CHANGEME",
    "time": "00",
    "type": "pf",
    "number": "1/to/32",
})

Re- forecasts used to calibrate a  real-time forecast:

Retrieving one field (total precipitation here) for all time steps and  for all the re-forecast used to calibrate the real-time forecast starting on 8 February 2015. For this request, all the re-forecasts starting on 6 February 1981-2013 and11 February 1981-2013 are retrieved

 #!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
 "class": "s2",
 "dataset": "s2s",
"hdate": "19810206/19820206/19830206/19840206/19850206/19860206/19870206/19880206/19890206/19900206/19910206/19920206/19930206/19940206/19950206/19960206/19970206/19980206/19990206/20000206/20010206/20020206/20030206/20040206/20050206/20060206/20070206/20080206/20090206/20100206/20110206/20120206/20130206",
 "expver": "prod",
 "levtype": "sfc",
 "origin": "ammc",
 "param": "tp",
 "step": "24/to/1488/by/24",
 "stream": "enfh",
 "target": "CHANGEME",
 "time": "00",
 "type": "cf",
" date": "20140101",
})
 #!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
 "class": "s2",
 "dataset": "s2s",
"hdate": "19810211/19820211/19830211/19840211/19850211/19860211/19870211/19880211/19890211/19900211/19910211/19920211/19930211/19940211/19950211/19960211/19970211/19980211/19990211/20000211/20010211/20020211/20030211/20040211/20050211/20060211/20070211/20080211/20090211/20100211/20110211/20120211/20130211",
 "expver": "prod",
 "levtype": "sfc",
 "origin": "ammc",
 "param": "tp",
 "step": "24/to/1488/by/24",
 "stream": "enfh",
 "target": "CHANGEME",
 "time": "00",
 "type": "cf",
" date": "20140101",
})


 #!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
 "class": "s2",
 "dataset": "s2s",
"hdate": "19810206/19820206/19830206/19840206/19850206/19860206/19870206/19880206/19890206/19900206/19910206/19920206/19930206/19940206/19950206/19960206/19970206/19980206/19990206/20000206/20010206/20020206/20030206/20040206/20050206/20060206/20070206/20080206/20090206/20100206/20110206/20120206/20130206",
 "expver": "prod",
 "levtype": "sfc",
 "origin": "ammc",
 "param": "tp",
 "step": "24/to/1488/by/24",
 "stream": "enfh",
 "target": "CHANGEME",
 "time": "00",
 "type": "pf",
 "number": "1/to/32",
" date": "20140101",
})


 #!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
 "class": "s2",
 "dataset": "s2s",
"hdate": "19810211/19820211/19830211/19840211/19850211/19860211/19870211/19880211/19890211/19900211/19910211/19920211/19930211/19940211/19950211/19960211/19970211/19980211/19990211/20000211/20010211/20020211/20030211/20040211/20050211/20060211/20070211/20080211/20090211/20100211/20110211/20120211/20130211",
 "expver": "prod",
 "levtype": "sfc",
 "origin": "ammc",
 "param": "tp",
 "step": "24/to/1488/by/24",
 "stream": "enfh",
 "target": "CHANGEME",
 "time": "00",
 "type": "pf",
 "number": "1/to/32",
" date": "20140101",
})