Issue with while loop and if statement

Question

Hey Im trying to make pretty simple app that check actual btc price and check if last_price is lower or higher then actual, but I cant figure out why is app stuck on this statement and keep spamming only this one:

    elif price > last_price:
  if last_price != price:
    print(Fore.GREEN + "Bitcoin price has increased: $", functions.getbtcprice())

Here is code: main.py

from btcapi import *
from colorama import Fore

def main(): 
  last_price = -1
  while True:
    price = functions.getbtcprice() 
    if last_price == -1:
      print("Bitcoin price: $",price)
      last_price = price
    elif price > last_price:
      if last_price != price:
        print(Fore.GREEN + "Bitcoin price has increased: $", functions.getbtcprice())
    elif price < last_price:
      if last_price != price:
        print(Fore.RED + "Bitcoin price has decreased: $", functions.getbtcprice())
     
if __name__ == "__main__":
    main()

and btcapi.py

import requests
import json

class functions:  
    def getbtcprice():   
        response = requests.get("https://api.coinbase.com/v2/prices/spot?currency=USD").text
        response_info = json.loads(response)
        return float(response_info["data"]["amount"])

Thats the problem:

https://imgur.com/a/WzDeByF

What Im trying to do is print first time actual btc price and the next one value different then the first one check if its lower or higher and print specififc values

Surely if price > last_price then last_price != price, so I don't se the point of explicitly checking that condition. — John Coleman
It's not really clear what you're trying to do. It keeps "spamming" that price because I suspect the price isn't changing by the millisecond -- which is how often you're getting the price from the API. You're likely going to get rate-limited because you are the one doing the spamming on that API. — ddejohn
@ddejohn im trying to check if last price is higher or lower than actual price from api — janGlin4171
I understand that, but you're doing it hundreds of times per second. What is the frequency at which BTC price actually varies? If it only changes value every 30 seconds, for instance, then you're not going to see any change for thousands of print statements. It's not clear why you're hitting the API as fast as you are. Again, you are likely going to get rate-limited by the API if you keep doing that, but if you really want to, then just add an if statement: if last_price == price: continue. — ddejohn
Also, you need to set last_price every time you hit the API. — ddejohn

ddejohn ddejohn · Accepted Answer · 2022-04-06T22:15:55

Your issue is that you are not setting the last_price anywhere in your for loop. You need to update the last_price to the current price before your loop ends, and before you get the next current price, so that you can compare the two. Nothing will be printed if the price hasn't changed.

Note that your nested if statements were redundant. The < and > operators return False if the two values are equal, so if they return True then it is implied that the two values are not equal, and is therefore unnecessary to check.

I suggest adding timestamps to your price increase/decrease statements. I also suggest adding a time.sleep() so that you're not hitting the API thousands of times per minute.

from btcapi import *
from colorama import Fore


def main(): 
  # Initialize current and previous prices
  current_price = functions.getbtcprice()
  last_price = current_price
  print("Bitcoin price: $", current_price)
  while True:
    if current_price > last_price:
      print(Fore.GREEN + "Bitcoin price has increased: $", current_price)
    elif current_price < last_price:
      print(Fore.RED + "Bitcoin price has decreased: $", current_price)
    # Set last_price to current_price, then update current_price
    last_price = current_price
    current_price = functions.getbtcprice()


if __name__ == "__main__":
    main()

Issue with while loop and if statement

1 Answers