import pandas as pd
from itertools import groupby
from collections import OrderedDict
import json

df = pd.read_csv('data8.csv', dtype={
            "Source" : str,
            "Template": str,
            "ConfigurationSetName": str,
       })

 results = []

for (Source, Template, ConfigurationSetName), bag in df.groupby      (["Source", "Template", "ConfigurationSetName"]):
   contents_df = bag.drop(["Source", "Template", "ConfigurationSetName"], axis=1)
Destinations = [OrderedDict(row) for i,row in contents_df.iterrows()]
results.append(OrderedDict([("Source", Source),
                            ("Template", Template),
                            ("ConfigurationSetName", ConfigurationSetName),
                            ("Destinations", Destinations)]))

print json.dumps(results[0], indent=4)
with open('ExpectedJsonFile.json', 'w') as outfile:
    outfile.write(json.dumps(results[0], indent=4))

Source,Template,ConfigurationSetName,ToAddresses,ReplacementTemplateData
 demo@example.com,MyTemplate,noreply,customer1@gmail.com,customer1
 demo@example.com,MyTemplate,noreply,customer2@gmail.com,customer2

{
    "Source": "demo@example.com",
    "Template": "MyTemplate",
    "ConfigurationSetName": "noreply",
    "Destinations": [
        {
            "ToAddresses": "customer1@gmail.com",
            "ReplacementTemplateData": "customer"
        },
        {
            "ToAddresses": "customer2@gmail.com",
            "ReplacementTemplateData": "customer2"
        }
    ]
}

{
  "Source":"demo@example.com",
  "Template":"MyTemplate",
  "ConfigurationSetName": "noreply",
  "Destinations":[
    {
      "Destination":{
        "ToAddresses":[
        "customer1@gmail.com"
       ]
    },
      "ReplacementTemplateData":"{ "name":"customer1" }"
    },
    {
      "Destination":{
        "ToAddresses":[
        "customer2@gmail.com"
       ]
    },
     "ReplacementTemplateData":"{ "name":"customer2" }"
    },
    {
      "Destination":{
       "ToAddresses":[
       "customer3@gmail.com"
     ]
    },
  "ReplacementTemplateData":"{}"
 }
 ],
 "DefaultTemplateData":"{ "name":"friend" }"
}

{
  "Template": {
  "TemplateName": "MyTemplate",
  "SubjectPart": "Greetings, {{Name}}!",
  "HtmlPart": "<h1>Hello {{Name}},</h1><p>Your favorite animal is cat.</p>",
  "TextPart": "Dear {{Name}},rnYour favorite animal is cat."
  }
}