How to define multiple error handling statements?

I would like to read a set of csv files from URL as dataframes. These files contain a date in their name like YYYYMMDD.csv in their names. I need to iterate over a set of predefined dates and read the corresponding file into a Python. Sometimes the file does not exist and an error as follows is thrown:

raise HTTPError(req.full_url, code, msg, hdrs, fp)

urllib.error.HTTPError: HTTP Error 404: Not Found

What I would do in this situation is to add one day to the date like turning 2020-05-01 to 2020-05-02 and in case of throwing the aforementioned error I would add 2 days to the date or at most 3 days until there is a url available without an error. I would like to know how I can write it in a program maybe with nested try - except where if adding 1 day to the date leads to a URL without error the subsequent steps are not executed.

As I don't have the data I will use the following URL as an example:

import pandas as pd
import requests

url = 'http://winterolympicsmedals.com/medals.csv'
s = requests.get(url).content
c = pd.read_csv(s)

Here the file being read is medals.csv. If you try madels.csv or modals.csv you will get the error I am talking about. So I need to know how I can control the errors in 3 steps by replacing the file name until I get the desired dataframe like first we try madels.csv resulting in an error, then models.csv also resulting in an error and after that medals.csv which result in the desired output.

My problem is that sometimes the modification I made to the file also fails in except so I need to know how I can accommodate a second modification.

Solution

No need to do any nested try-except blocks, all you need is one try-except and a for loop.

First, function that tries to read a file (returns content of the file, or None if the file is not found):

def read_file(fp):

    try:
        with open(fp, 'r') as f:
            text = f.read()
            return text
    
    except Exception as e:
        print(e)
        return None

Then, function that tries to find a file from a predefined date (example input would be '20220514'). The functions tries to read content of the file with the given date, or dates up to 3 days after it:

from datetime import datetime, timedelta

def read_from_predefined_date(date):

    date_format = '%Y%m%d'
    date = datetime.strptime(date, date_format)

    result = None
    for i in range(4):

        date_to_read = date + timedelta(days=i)
        date_as_string = date_to_read.strftime(date_format)
        fp = f'data/{date_as_string}.csv'
        result = read_file(fp)

        if result:
            break

    return result

To test, e.g. create a data/20220515.csv and run following code:

d = '20220514'
result = read_from_predefined_date(d)