Syntax to use to make “minus x days” with Python 3.8?

问题

    import pandas as pd
    import requests
    from bs4 import BeautifulSoup
    import time
    import datetime
    from datetime import date, timedelta

    # MM/DD/YYYY : time.strftime("%m/%d/%Y")
    # YYYYMMDD : time.strftime('%Y%m%d')

if datetime.datetime.now().isoweekday() == 1 : # If today is a Monday -> some dates must be minus 3 days to take the previous Friday's data

    url_DAX = 'https://www.eurexchange.com/exchange-en/market-data/statistics/market-statistics-online/100!onlineStats?viewType=4&productGroupId=13394&productId=34642&cp=&month=&year=&busDate=' + str(time.strftime('%Y%m%d') - timedelta(days=3))   #Should be minus 3 days
    df = pd.read_html(url_DAX)[0]
    df.to_csv('results_DAX_' + str(time.strftime('%Y%m%d')) + '.csv') 
    print(df)

This give me the following error :

 url_DAX = 'https://www.eurexchange.com/exchange-en/market-data/statistics/market-statistics-online/100!onlineStats?viewType=4&productGroupId=13394&productId=34642&cp=&month=&year=&busDate=' + str(time.strftime('%Y%m%d') - timedelta(days=2))  # Should be minus 2 days
TypeError: unsupported operand type(s) for -: 'str' and 'datetime.timedelta'

I'd like to know how to write this correctly as I need to have the final date (after the minus 1, 2 or 3 days) in the following format : YYYYMMDD.

Thanks

回答1:

Do the subtraction in a separate statement:

from datetime import date, timedelta
dt = date.today() - timedelta(days=2)

Then convert it to a string in your format

busdate =  dt.strftime('%Y%m%d')
url_DAX = 'https://www.eurexchange.com/exchange-en/market-data/statistics/market-statistics-online/100!onlineStats?viewType=4&............&busDate=' + busdate

回答2:

You can use datetime module. Make datetime instance and then add timedelta you want to:

dtm += datetime.timedelta(hours=2)

来源：https://stackoverflow.com/questions/58901554/syntax-to-use-to-make-minus-x-days-with-python-3-8