Element Tree Xpath

hey_arnold · (This post was last modified: Aug-05-2018, 09:41 AM by hey_arnold.)

I am trying to extract certain data from the XML using Element tree, but I am unsure why my code doesn't work, any guidance would be helpful.

It appears that the paths I have used aren't correct as no values are returned. I think I am fairly close..... hopefully?

import requests
from lxml import etree
     
fromDate = "2018-07-29"
 
def getXML():
    url="http://energywatch.natgrid.co.uk/EDP-PublicUI/PublicPI/InstantaneousFlowWebService.asmx"
    headers = {'content-type': 'application/soap+xml; charset=utf-8'}
    body ="""<soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
  <soap12:Body>
    <GetInstantaneousFlowData xmlns="http://www.NationalGrid.com/EDP/UI/" />
  </soap12:Body>
</soap12:Envelope>"""
 
    response = requests.post(url,data=body,headers=headers)
    return response.content
 
import pandas as pd
df1 = pd.DataFrame(columns=("applicable_at","name","value","created_date"))   
for pd_date in pd.date_range(fromDate, periods=1):
    day = pd_date.strftime('%Y-%m-%d')
      
    root = etree.fromstring(getXML())
    #map prefix 'd' to the default namespace URI
    ns = {'d': 'http://www.nationalgrid.com/EDP/BusinessEntities/Public'}
      
    publication_objects = root.xpath('//d:EDPObjectCollection', namespaces=ns)
      
    for obj in publication_objects:
        name = obj.find('d:EDPObjectName', ns).text
      
        for data in obj.findall('d:EnergyDataList/d:EDPEnergyDataBE', ns):
            applicable_at = pd.to_datetime(data.find('d:ApplicableAt', ns).text)    
            value = float(data.find('d:FlowRate', ns).text)
            created_date = pd.to_datetime(data.find('d:ScheduleTime', ns).text)
 
         
          
            df1.loc[len(df1) +1] = [applicable_at,name, value,created_date]

wavic · Aug-05-2018, 11:17 AM

Did you check if response.content contains the expected data?

hey_arnold · (This post was last modified: Aug-05-2018, 11:33 AM by hey_arnold.)

Yep. I printed response.content and it contains the XML that I need.

The problem is to do with the paths I have set element tree to look at. I think they might not Ben right.

wavic · Aug-05-2018, 11:45 AM

The response is returned as bytes. What happens if you convert it to string?

hey_arnold · Aug-05-2018, 11:55 AM

It should work as bytes. It’s something to do with the xml structure and how I’m trying to extract it

wavic · Aug-05-2018, 12:25 PM

The code "doesn't work" how? Getting error, do not get a result?

hey_arnold · (This post was last modified: Aug-05-2018, 07:48 PM by hey_arnold.)

(Aug-05-2018, 12:25 PM)wavic Wrote: The code "doesn't work" how? Getting error, do not get a result?

Here is a working example of what I want to do. However with the example I am stuck on, the XML returned from the API has a more complicated structure and when I try and get Element tree to pickup certain elements of the tree, it won't do it.

Working Example:

import requests
from lxml import etree
toDate = "2018-04-25"
fromDate = "2018-04-25"
dateType = "gasday"

def getXML():
    url="http://marketinformation.natgrid.co.uk/MIPIws-public/public/publicwebservice.asmx"
    headers = {'content-type': 'application/soap+xml; charset=utf-8'}
    body ="""<soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
        <soap12:Body>
            <GetPublicationDataWM xmlns="http://www.NationalGrid.com/MIPI/">
                <reqObject>
                    <LatestFlag>Y</LatestFlag>
                    <ApplicableForFlag>Y</ApplicableForFlag>
                    <ToDate>%s</ToDate>
                    <FromDate>%s</FromDate>
                    <DateType>%s</DateType>
                    <PublicationObjectNameList>
                    <string>Nominations, Prevailing Nomination, STFergus-NSMP, Sub Terminal</string>
                    <string>Nominations, Prevailing Nomination, Stublach, Storage Entry</string>
                    <string>Nominations, Prevailing Nomination, Stublach, Storage Exit</string>
                    <string>Nominations, Prevailing Nomination, Teesside-BP, Sub Terminal</string>
                    <string>Nominations, Prevailing Nomination, Teesside-PX, Sub Terminal</string>
                    <string>Nominations, Prevailing Nomination, Theddlethorpe, Sub Terminal</string>
                    </PublicationObjectNameList>
                </reqObject>
            </GetPublicationDataWM>
        </soap12:Body>
    </soap12:Envelope>""" % (toDate, fromDate,dateType)

    response = requests.post(url,data=body,headers=headers)
    return response.content
root = etree.fromstring(getXML())
# map prefix 'd' to the default namespace URI
ns = { 'd': 'http://www.NationalGrid.com/MIPI/'}
 

import pandas as pd

df1 = pd.DataFrame(columns=("applicable_at","applicable_for","name","value","quality_indicator","substituted","created_date"))   
for pd_date in pd.date_range(fromDate, periods=1):
    day = pd_date.strftime('%Y-%m-%d')
     
    root = etree.fromstring(getXML())
     
    #map prefix 'd' to the default namespace URI
    ns = {'d': 'http://www.NationalGrid.com/MIPI/'}
     
    publication_objects = root.xpath('//d:CLSMIPIPublicationObjectBE', namespaces=ns)
     
    for obj in publication_objects:
        name = obj.find('d:PublicationObjectName', ns).text
     
        for data in obj.findall('d:PublicationObjectData/d:CLSPublicationObjectDataBE', ns):
            applicable_at = pd.to_datetime(data.find('d:ApplicableAt', ns).text)    
            applicable_for = pd.to_datetime(data.find('d:ApplicableFor', ns).text)
            value = float(data.find('d:Value', ns).text)
            quality_indicator = data.find('d:Value', ns).text
            substituted = data.find('d:Substituted', ns).text
            created_date = pd.to_datetime(data.find('d:CreatedDate', ns).text)
        
         
            df1.loc[len(df1) +1] = [applicable_at, applicable_for,name, value, quality_indicator, substituted, created_date]

My none working example:

import requests
from lxml import etree
      
fromDate = "2018-07-29"
  
def getXML():
    url="http://energywatch.natgrid.co.uk/EDP-PublicUI/PublicPI/InstantaneousFlowWebService.asmx"
    headers = {'content-type': 'application/soap+xml; charset=utf-8'}
    body ="""<soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
  <soap12:Body>
    <GetInstantaneousFlowData xmlns="http://www.NationalGrid.com/EDP/UI/" />
  </soap12:Body>
</soap12:Envelope>"""
  
    response = requests.post(url,data=body,headers=headers)
    return response.content
  
import pandas as pd
df1 = pd.DataFrame(columns=("applicable_at","name","value","created_date"))   
for pd_date in pd.date_range(fromDate, periods=1):
    day = pd_date.strftime('%Y-%m-%d')
       
    root = etree.fromstring(getXML())
    #map prefix 'd' to the default namespace URI
    ns = {'d': 'http://www.nationalgrid.com/EDP/BusinessEntities/Public'}
       
    publication_objects = root.xpath('//d:EDPObjectCollection', namespaces=ns)
       
    for obj in publication_objects:
        name = obj.find('d:EDPObjectName', ns).text
       
        for data in obj.findall('d:EnergyDataList/d:EDPEnergyDataBE', ns):
            applicable_at = pd.to_datetime(data.find('d:ApplicableAt', ns).text)    
            value = float(data.find('d:FlowRate', ns).text)
            created_date = pd.to_datetime(data.find('d:ScheduleTime', ns).text)
  
          
           
            df1.loc[len(df1) +1] = [applicable_at,name, value,created_date]

Have I set the correct namespace and root path in order to extract data from EDPObjectName?

wavic · (This post was last modified: Aug-05-2018, 09:58 PM by wavic.)

Well, I managed to get a non-empty publication_objects list.
I don't know how I did it. I am not using lxml and xpath is almost magic for me.
However here it is ( some print functions are added for my convenience ):

import requests
from lxml import etree

fromDate = "2018-07-29"

def getXML():
    url="http://energywatch.natgrid.co.uk/EDP-PublicUI/PublicPI/InstantaneousFlowWebService.asmx"
    headers = {'content-type': 'application/soap+xml; charset=utf-8'}
    body ="""<soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
  <soap12:Body>
    <GetInstantaneousFlowData xmlns="http://www.NationalGrid.com/EDP/UI/" />
  </soap12:Body>
</soap12:Envelope>"""

    response = requests.post(url,data=body,headers=headers)
    print(response.content)
    return response.content

import pandas as pd
df1 = pd.DataFrame(columns=("applicable_at","name","value","created_date"))
for pd_date in pd.date_range(fromDate, periods=1):
    day = pd_date.strftime('%Y-%m-%d')

    root = etree.fromstring(getXML())
    print(root)
    #map prefix 'd' to the default namespace URI
    ns = {'soap': 'http://www.NationalGrid.com/EDP/BusinessEntities/Public'}

    publication_objects = root.xpath('//soap:EDPObjectCollection', namespaces=ns)
    print('\n\n')
    print(publication_objects)

    for obj in publication_objects:
        name = obj.find('soap:EDPObjectName', ns).text()

        for data in obj.findall('soap:EnergyDataList/d:EDPEnergyDataBE', ns):
            applicable_at = pd.to_datetime(data.find('d:ApplicableAt', ns).text)
            value = float(data.find('soap:FlowRate', ns).text)
            created_date = pd.to_datetime(data.find('soap:ScheduleTime', ns).text)



            df1.loc[len(df1) +1] = [applicable_at,name, value,created_date]

It produces another error but I am too tired. It's an hour after midnight here.

hey_arnold · Aug-06-2018, 05:33 PM

Thanks for your help so far, I haven't had a chance to take a look at the what you posted up as I have been super busy. I will try and take a look this evening.

hey_arnold · (This post was last modified: Aug-09-2018, 02:53 PM by hey_arnold.)

Does that mean something further up in my code didnt work correctly?

Here is my error:

Error:Traceback (most recent call last):
  File "python", line 34, in <module>
AttributeError: 'NoneType' object has no attribute 'text'

import requests
from lxml import etree
 
fromDate = "2018-07-29"
 
def getXML():
    url="http://energywatch.natgrid.co.uk/EDP-PublicUI/PublicPI/InstantaneousFlowWebService.asmx"
    headers = {'content-type': 'application/soap+xml; charset=utf-8'}
    body ="""<soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
  <soap12:Body>
    <GetInstantaneousFlowData xmlns="http://www.NationalGrid.com/EDP/UI/" />
  </soap12:Body>
</soap12:Envelope>"""
 
    response = requests.post(url,data=body,headers=headers)
    print(response.content)
    return response.content
 
import pandas as pd
df1 = pd.DataFrame(columns=("applicable_at","name","value","created_date"))
for pd_date in pd.date_range(fromDate, periods=1):
    day = pd_date.strftime('%Y-%m-%d')
 
    root = etree.fromstring(getXML())
    print(root)
    #map prefix 'd' to the default namespace URI
    ns = {'soap': 'http://www.NationalGrid.com/EDP/BusinessEntities/Public'}
 
    publication_objects = root.xpath('//soap:EDPObjectCollection', namespaces=ns)
    print('\n\n')
    print(publication_objects)
 
    for obj in publication_objects:
        name = obj.find('soap:EDPObjectName', ns).text()
 
        for data in obj.findall('soap:EnergyDataList/d:EDPEnergyDataBE', ns):
            applicable_at = pd.to_datetime(data.find('d:ApplicableAt', ns).text)
            value = float(data.find('soap:FlowRate', ns).text)
            created_date = pd.to_datetime(data.find('soap:ScheduleTime', ns).text)
 
 
 
            df1.loc[len(df1) +1] = [applicable_at,name, value,created_date]

Could it be something to do with when the api response is parsed with etree?

Element Tree Xpath

User Panel Messages

Announcements