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Overview

alto.yml
...
download_files:
  - "output1.csv"
  - "output2.csv"
...
The download_files key should contain the list of files to download from the cloud environment after the code successfully executes. Alto runs your code on the cloud environment exactly as it runs on your local machine — so, if your code outputs files when run locally, those will also get created within your cloud environment. The download_files allows you to access these files. For example, suppose your script looks something like this (this pulls top stories from the HackerNews API):
hacker_news.py
from pathlib import Path
import requests
from typing import List

def get_live_data_item_ids(base_url: str, hn_stories: str, thres: int) -> List[str]:
    """
    Get item IDs associated with `hn_stories`. Note that `hn_stories` must be an
    acceptable GET request via the Hacker News live data API. See more here:
    https://hackernews.api-docs.io/v0/live-data/max-item-id

    args:
        base_url: URL used for API requests
        hn_stories: live data GET request
        thres: how many IDs to retrieve; -1 means all IDs are retrieved
    returns:
        list of Hacker News story IDs
    """
    stories_url = base_url + hn_stories
    payload = {}
    response = requests.request('GET', stories_url, data=payload)
    story_ids_txt = response.text
    story_ids_list = story_ids_txt.replace('[', '').replace(']', '').replace(' ', '').split(',')
    if thres==-1:
        return story_ids_list
    else:
        return story_ids_list[:thres]


def get_story_from_id(id_url: str, item_id: str) -> pd.DataFrame:
    """
    In the Hacker News API, stories, comments, jobs, Ask HNs and even polls are just items. 
    They're identified by their ids, which are unique integers, and live under
    https://hacker-news.firebaseio.com/v0/item/{item-id}

    args:
        id_url: URL used for requesting items from individual ID
        id: item ID represented as a string
    returns:
        response JSON as a dictionary
    """
    # url = prism_project.ID_URL
    payload = "{}"
    response = requests.request("GET", id_url.format(item_id=item_id), data=payload)
    response_dict = json.loads(response.text)

    # Convert dictionary to a DataFrame
    df = pd.DataFrame({k: [v] for k,v in response_dict.items()})

    # Confirm df has one row
    assert df.shape[0]==1, prism_project.PRISM_LOGGER.error("bad response dictionary")
    return df


if __name__ == "__main__":
    # Constants
    BASE_URL = "https://hacker-news.firebaseio.com/v0/"
    ID_URL = "https://hacker-news.firebaseio.com/v0/item/{item_id}.json"
    REQUEST = 'topstories.json'
    STORY_THRESHOLD = 100000
    UPVOTE_THRESH = 50
    COMMENT_THRESH = 1
    
    # IDs
    live_data_ids = get_live_data_item_ids(BASE_URL, REQUEST, STORY_THRESHOLD)
    print(f'Extracted IDs for `{REQUEST}`')
    
    # Stories
    temp_dfs = []
    for storyid in live_data_ids:
        temp_story_df = self.get_story_from_id(ID_URL, str(storyid))
        temp_dfs.append(temp_story_df)
    live_data_df = pd.concat(temp_dfs)
    print(f'Got stories for `{REQUEST}`')
    
    # Write the data
    live_data_df.to_csv(Path(__file__).parent / 'output' / 'topstores.csv')
The script writes a file to a local folder called output that lives in the same directory as the script. The file is called topstories.csv. If we wanted to create this file using Alto and then download it after it was successfully created, we could specify our configuration as follows:
alto.yml
...
download_files:
  - "output/topstories.csv"
...
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