As per your documentation the response structure is invalid.
data.last_price is incorrect, as you can see from the structure of the response.
Also the value NSE_FO:NIFTY2543021600PE where do we get this from because according to the documentation we are passing the instrument_token: **NSE_FO|51834.
**
Pleas suggest a solution
use this
url = “https://api.upstox.com/v3/market-quote/ltp”
params = {“instrument_key”: “NSE_FO|51834”}
headers = {“Authorization”: f"Bearer {access_token}", “Accept”: “application/json”}
response = requests.get(url, headers=headers, params=params)