我如何从 Python 函数返回多个变量

Question

I have a function that extracts a string from a website, the function is as follows:

def get_maps_info(url):
page = get_parsed_page(url)
# extract match infos 
maps = page.find('div', {'class' : 'padding preformatted-text'})
return maps.text

The code above will returning something like this:

'Best of 1\n\n* Group B elimination match'

So I have another function that checks, if find 'Best of 3' starts the first 'if', i am very newbie in python, but i think this is ok, if u have some tips or best practice please show me.

The problem is i need to return all this variables, how i can do this?

def get_results_maps(url):
page = get_parsed_page(url)

if 'Best of 3' in get_maps_info(url):
    ## verify team winners for each map for Best of 3
    ## first team is the winner and second is the loser and so on
    if int(page.findAll('div', {'class' : 'results-team-score'})[0].text)>=int(page.findAll('div', {'class' : 'results-team-score'})[1].text):
        team_winner_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text) 
        team_loser_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text)   
    else:
        team_winner_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text)
        team_loser_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text) 

    if int(page.findAll('div', {'class' : 'results-team-score'})[2].text)>=int(page.findAll('div', {'class' : 'results-team-score'})[3].text):
        team_winner_map2 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text)
        team_loser_map2 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text)
    else:
        team_winner_map2 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text)
        team_loser_map2 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text)

    if int(page.findAll('div', {'class' : 'results-team-score'})[4].text)>=int(page.findAll('div', {'class' : 'results-team-score'})[5].text):
        team_winner_map3 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text)
        team_loser_map3 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text) 
    else:
        team_winner_map3 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text)
        team_loser_map3 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text)

    # end verify team winners for each map for Best of 3

    ## verify team winners for each map for Best of 1
elif 'Best of 1' in get_maps_info(url):
    if int(page.findAll('div', {'class' : 'results-team-score'})[0].text)>=int(page.findAll('div', {'class' : 'results-team-score'})[1].text):
        team_winner_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text) 
        team_loser_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text)   
    else:
        team_winner_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[1].text)
        team_loser_map1 = (page.findAll('div', {'class' : 'results-teamname text-ellipsis'})[0].text) 
    # end verify team winners for each map for Best of 1    

return (team_winner_map1, team_loser_map1, team_winner_map2, team_loser_map2, team_winner_map3, team_loser_map3)

error after i run the function above:

I don't know if I was clear enough, otherwise feel free to ask about anything to me.

Answer 1

The issue you have is that not all of the variables you're using in your return statement are created in the code above. There are a few ways that can happen.

To begin with, if neither Best of 1 nor Best of 3 appear, you won't define any of the variables. That's obviously bad, and might indicate that your data isn't entirely in the format you expect. You might diagnose that situation by adding an else section to your existing if / elif branches. Even if it's not supposed to ever happen, it's often worth checking every possibility and at least reporting the error in a good way.

The other issue is that your if and elif options define different sets of variables. Your current code expects all three pairs of winning and losing scores, but in the Best of 1 case, it will only find the first pair. To fix this, you either need to customize the return statement for each branch (so the best of 1 case can return a 2-tuple rather than a 6-tuple), or you need to define dummy values for the games that never occurred. (I'm also not sure if you'll always get three game results in a best of 3, but that's a different issue.)

A minor issue (that might or might not be a big deal, depending on how code you haven't shown is implemented) is that you're repeatedly calling the get_maps_info function in the different tests for your if / elif That may be inefficient if it needs to fetch the URL from the web each time. A better approach might be to save the results of just one call and reuse it as necessary (as you're already doing with page ).

Putting this all together, I'd structure the code something more like:

page = get_parsed_page(url)
maps_info = get_maps_info(url)

if 'Best of 3' in maps_info:
    ...     # code to find winner/loser stuff omitted for brevity

    return (team_winner_map1, team_loser_map1,
            team_winner_map2, team_loser_map2,
            team_winner_map3, team_loser_map3) # move the current return statement here!

elif 'Best of 1' in maps_info:
    ...

    return (team_winner_map1, team_loser_map1) # return a 2-tuple in this case

else:  # report error if we don't get any of the strings we expect
    raise ValueError("Expected Best of 3 or Best of 1, got map-info: {!r}".format(map_info))