How to retrieve only the first 2 data from a specific REST endpoint (no the entire data) Python

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How to retrieve only the first 2 data from a specific REST endpoint instead of all the data in the HTTP?

My input:

import requests
import json

url = "https://ws1.chic.ulster.ac.uk/SensorCentral/REST/SensorDataRangeNanos/flgSh9oHnutzvZVOnnixFNjXIda2zula_101_101?startTs=1594297110372000000&endTs=1594297110372000000"

response = requests.get(url)
data = response.text
parsed = json.loads(data)

print(json.dumps(parsed, indent=1))

where my output (which listed all the elements):

[
 {
  "sensorClass": 101, 
  "uID": "flgSh9oHnutzvZVOnnixFNjXIda2zula_101_101", 
  "eventCode": 101, 
  "sensorUUID": "flgSh9oHnutzvZVOnnixFNjXIda2zula", 
  "timeStamp": 1.594297110372e+18, 
  "deviceMfg": 101, 
  "blobJson": "[{'deviceTimestamp': 166150, 'x': 3.8919, 'y': -8.6865, 'z': -3.3077}, {'deviceTimestamp': 166170, 'x': 4.2998, 'y': -9.8624, 'z': -2.0769}, {'deviceTimestamp': 166190, 'x': 0.74341, 'y': -9.4483, 'z': 0.57692}, {'deviceTimestamp': 166210, 'x': 0.73178, 'y': -9.5004, 'z': 3.0769}, {'deviceTimestamp': 166230, 'x': 3.5538, 'y': -9.7006, 'z': 3.3077}, {'deviceTimestamp': 166250, 'x': -1.4629, 'y': -7.0692, 'z': 2.2308}, {'deviceTimestamp': 166260, 'x': -6.7571, 'y': -5.0299, 'z': -0.076923}, {'deviceTimestamp': 166280, 'x': -5.0319, 'y': -6.5896, 'z': -0.076923}, {'deviceTimestamp': 166300, 'x': -0.21122, 'y': -8.9002, 'z': 2.5}, {'deviceTimestamp': 166320, 'x': 6.3477, 'y': -9.3142, 'z': 4.5385}, {'deviceTimestamp': 166340, 'x': 10.904, 'y': -9.9498, 'z': 5.6538}, {'deviceTimestamp': 166360, 'x': 9.5501, ............................................(ALL THE DATA)

However, I want to get the out which is only contains 2 records within the blobJson string.

I want to get output as:

[
 {
  "sensorClass": 101, 
  "uID": "flgSh9oHnutzvZVOnnixFNjXIda2zula_101_101", 
  "eventCode": 101, 
  "sensorUUID": "flgSh9oHnutzvZVOnnixFNjXIda2zula", 
  "timeStamp": 1.594297110372e+18, 
  "deviceMfg": 101, 
  "blobJson": "[{'deviceTimestamp': 166150, 'x': 3.8919, 'y': -8.6865, 'z': -3.3077}, {'deviceTimestamp': 166170, 'x': 4.2998, 'y': -9.8624, 'z': -2.0769}]"
 }
]

which only 2 element in blobJson

What I have tried:

import requests
import json

url = "https://ws1.chic.ulster.ac.uk/SensorCentral/REST/SensorDataRangeNanos/flgSh9oHnutzvZVOnnixFNjXIda2zula_101_101?startTs=1594297110372000000&endTs=1594297110372000000"

response = requests.get(url)
data = response.text
parsed = json.loads(data)

print(json.dumps(parsed, indent=1))

Posted 17-Jul-20 1:16am

Member 14891535

Updated 28-Jul-20 3:25am

v3

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Comments

Richard MacCutchan 17-Jul-20 8:46am

You don't get a choice, you get whatever the server sends based on your query.

Member 14891535 17-Jul-20 9:32am

But can I set which one to printout?

Richard MacCutchan 17-Jul-20 9:39am

Yes, but you need to write the code to extract the part that you want.

Member 14891535 17-Jul-20 9:40am

Any idea can advice? which I struggle in

Richard MacCutchan 17-Jul-20 9:46am

Yes, go to json — JSON encoder and decoder — Python 3.8.4 documentation[^] and you will find all the information you need on handling JSON.

Member 14891535 17-Jul-20 10:35am

Thanks. I did had a tried, but cannot get which library should I used.

Member 14891535 17-Jul-20 10:35am

print(json.dumps(parsed, indent=1))

Richard MacCutchan 17-Jul-20 12:09pm

What do you mean "what library"? JSON support is built in to Python as explained in that page of the documentation.

Member 14891535 17-Jul-20 12:22pm

Oh, okay, maybe the words that I used incorrect. But I still unable to figure out

Richard MacCutchan 17-Jul-20 12:33pm

Sorry, but I really do not understand what you are trying to do. Please use the Improve question link above and explain clearly what data you are trying to get out of the response data.

Member 14891535 17-Jul-20 12:41pm

Thanks, I had improved my question. Hope is better

Richard MacCutchan 17-Jul-20 12:50pm

You most likely need to use the json.loads deserialize method to convert the text into Python constructs. You can then extract the items you want by reference to their positions in the list. You can print the result of the json.loads call, to see how to reference each item.

Member 14891535 17-Jul-20 13:04pm

yes, i did used parsed = json.loads(data)

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daubrecq · Answer 1 · 2020-07-28T03:25:00

Do as follows.

Python

import requests
import json

url = "https://ws1.chic.ulster.ac.uk/SensorCentral/REST/SensorDataRangeNanos/flgSh9oHnutzvZVOnnixFNjXIda2zula_101_101?startTs=1594297110372000000&endTs=1594297110372000000"

response = requests.get(url)
data = response.text
parsed = json.loads(data)
# new
# Get only the 2 first "blobJson" elements
blobJsonData = (parsed[0]["blobJson"])
json_formated_data = blobJsonData.replace("'", "\"")
json_data = json.loads(json_formated_data)
json_data_filtered = json_data[0:2]

# Update the data struct
parsed[0]["blobJson"] = json.dumps(json_data_filtered).replace("\"", "'")
# new

print(json.dumps(parsed, indent=1))