How to add two different elements from the same array which changes dynamically?

Question

I want to find the difference between the last element and the second last element of the array where the array changes dynamically.

Please go through the code.

import requests
import json
from bs4 import BeautifulSoup as bs
import datetime, threading
LTP_arr=[]
url = 'https://nseindia.com/live_market/dynaContent/live_watch/get_quote/GetQuoteFO .jsp?underlying=RELIANCE&instrument=FUTSTK&expiry=30MAY2019&type=-&strike=-'

def ltw():
    resp = requests.get(url)
    soup = bs(resp.content, 'lxml')
    data = json.loads(soup.select_one('#responseDiv').text.strip())
    LTP=data['data'][0]['lastPrice']
    LTP_arr.append(LTP)
    print(LTP_arr)
    threading.Timer(1, tvwap).start()   

ltw()

At a particular time if the array is LTP_arr=['34','65','66','32','81'] Output should be given as 49. Then on next time frame if the LTP_arr=['34','65','66','32','81','100'] output sholuld be shown as 19

What is ltw()? Your code is very poorly formatted. However, use int(LTP_arr[-1])-int(LTP_arr[-2]). Surround the expression with abs() if you want the absolute value. — 101arrowz
– 101arrowz, Commented May 23, 2019 at 19:08
Indenting is important in python. Please reformat your code. I don't know when you function ends. — Error - Syntactical Remorse
– Error - Syntactical Remorse, Commented May 23, 2019 at 19:09

Wilfried · Accepted Answer · 2019-05-23 19:15:28Z

2

You can access last element with [-1] LTP_arr[-1] give you '81', which is a string. Cast with int() You can do the same thing with [-2]

int(LTP_arr[-1]) - int(LTP_arr[-2])

You can add a try / except if your value can be cast by int()

try:
    int(LTP_arr[-1]) - int(LTP_arr[-2])
except IndexError:
    # do what you want to handle this error

edited May 23, 2019 at 19:15

answered May 23, 2019 at 19:10

Wilfried

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2 Comments

Error - Syntactical Remorse Over a year ago

You will want a try/except for IndexError as well.

Wilfried Over a year ago

I edit my post :) But sometimes you are sure about the data type. So try/except can be avoid if you know the data source

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