Visual Studio Code – Why is my python script working sometimes but not others? There seems to be a delay for it to work

HI i have put the below code together to look at the previous days high and low and then compare it to the day before to see what type of day it is with regards to the stock market.

I am having trouble though with it working consistently and can figure out why.

The error which comes back is below, after the code, however after about 5 minutes it then works, its very strange and I cant figure out what the issue is.

I’m using visual studio and I must admit this is the first time I have used python so there may be something obvious but I would really appreciate the advice from those who know more.

import yfinance as yf
import pandas as pd
from datetime import datetime, timedelta
import requests
from bs4 import BeautifulSoup

# Function to fetch S&P 500 tickers from Wikipedia
def fetch_sp500_tickers():
    url = "https://en.wikipedia.org/wiki/List_of_S%26P_500_companies"
    response = requests.get(url)
    soup = BeautifulSoup(response.text, 'html.parser')
    table = soup.find('table', {'class': 'wikitable'})
    tickers = []
    for row in table.find_all('tr')[1:]:
        ticker = row.find_all('td')[0].text.strip()
        tickers.append(ticker)
    return tickers

# List of known bank holidays
bank_holidays = [
    datetime(2025, 1, 1).date(),
    datetime(2025, 1, 20).date(),
    datetime(2025, 2, 17).date(),
    datetime(2025, 4, 18).date(),
    datetime(2025, 5, 26).date(),
    datetime(2025, 6, 19).date(),
    datetime(2025, 7, 4).date(),
    datetime(2025, 9, 1).date(),
    datetime(2025, 11, 27).date(),
    datetime(2025, 12, 25).date()
]

# Calculate last three unique market open days excluding today
today = datetime.now().date()
last_three_days = []
for i in range(1, 4):
    day = today - timedelta(days=i)
    while day.weekday() >= 5 or day in bank_holidays:
        day -= timedelta(days=1)
    last_three_days.append(day)

# Fetch S&P 500 tickers
tickers = fetch_sp500_tickers()

# Processing each ticker
for ticker in tickers:
    try:
        # Fetch data from the last 3 days
        start_date = last_three_days[2]
        end_date = today
        data_full = yf.download(ticker, start=start_date, end=end_date)

        # Ensure there are at least two days of data
        if len(data_full) < 2:
            print(f"{ticker} - Not enough data")
            continue

        # Get the high values for the two closest days to today
        high_day_1 = data_full['High'].iloc[-2] if len(data_full) >= 2 else None
        high_day_2 = data_full['High'].iloc[-1] if len(data_full) >= 1 else None

        # Get the low values for the two closest days to today
        low_day_1 = data_full['Low'].iloc[-2] if len(data_full) >= 2 else None
        low_day_2 = data_full['Low'].iloc[-1] if len(data_full) >= 1 else None

        # Calculate differences
        difference_high = float(high_day_2.iloc[0]) - float(high_day_1.iloc[0]) if high_day_1 is not None and high_day_2 is not None else None
        difference_low = float(low_day_2.iloc[0]) - float(low_day_1.iloc[0]) if low_day_1 is not None and low_day_2 is not None else None

        # Check condition
        if difference_high is not None and difference_low is not None:
            if difference_high < 0 and difference_low > 0:
                result = "Inside Day"
            elif difference_high > 0 and difference_low < 0:
                result = "Outside Day"
            elif difference_high > 0 and difference_low > 0:
                result = "2 Up"
            elif difference_high < 0 and difference_low < 0:
                result = "2 Down"
            else:
                result = "No Pattern"
            print(f"{ticker} - High difference: {difference_high:.2f}, Low difference: {difference_low:.2f}, Pattern: {result}")
        else:
            print(f"{ticker} - Insufficient data for pattern recognition")

    except Exception as e:
        print(f"{ticker} - Error: {e}") 

The error is:

1 Failed download:
[‘ABT’]: JSONDecodeError(‘Expecting value: line 1 column 1 (char 0)’)
ABT – Not enough data
[100%**] 1 of 1 completed

Ideally I would like to just run the script however the delay is making this very difficult to do.