python api to launch template unknown name cannot find field

Question

I've created and run a DataPrep job, and am trying to use the template from python on app engine. I can successfully start a job using

gcloud dataflow jobs run 
    --parameters "inputLocations={\"location1\":\"gs://bucket/folder/*\"},
outputLocations={\"location1\":\"project:dataset.table\"},
customGcsTempLocation=gs://bucket/DataPrep-beta/temp"
--gcs-location gs://bucket/DataPrep-beta/temp/cloud-dataprep-templatename_template

however trying to use python on app engine;

service = build('dataflow', 'v1b3', credentials=credentials)
input1  = {"location1": "{i1}".format(i1=input)}
output1 = {"location1": "{o1}".format(o1=output)}

print('input location: {}'.format(input1))

GCSPATH="gs://{bucket}/{template}".format(bucket=BUCKET, template=template)
BODY = {
    "jobName": "{jobname}".format(jobname=JOBNAME),
    "parameters": {
        "inputLocations":  input1,
        "outputLocations": output1,
        "customGcsTempLocation": "gs://{}/DataPrep-beta/temp".format(BUCKET)
     }
}

print("dataflow request body: {}".format(BODY))
request = service.projects().templates().launch(projectId=PROJECT, gcsPath=GCSPATH, body=BODY)
response = request.execute()

I get back;

"Invalid JSON payload received. Unknown name "location1" at 
  'launch_parameters.parameters[1].value': Cannot find field.
Invalid JSON payload received. Unknown name "location1" at 
  'launch_parameters.parameters[2].value': Cannot find field."

Nothing I've tried seems to support passing a dict or a json.dumps() or a str() to "inputLocations" or "outputLocations".

Answer 1

The issue is with the format that you are passing input1 and output1. They need to be between quotation marks like this:

input1 = '{"location1":"' + input + '" }'
output1 = '{"location1":"' + output + '" }'

I have tried sending the request with the same approach than you and it fails. It also fails if I later parse it back to string or json because it doesn't parse quotes correctly.