Counting using if inside for loop

Question

I'm using this repository:

https://github.com/fivethirtyeight/data/blob/master/avengers/avengers.csv

For an exercise in DataQuest, I have to count the number of 'Years since joining' is correct by subtracting 2015 (reference year) from column 'Year'.

I'm trying to use a for and if loop to do this simple task but I am having a hard time figuring out. How do I incorporate the 'for row' into the loop?

def Years_joined():    
    joined_accuracy_count = 0

    for row in avengers['Years since joining']:
        if (2015 - avengers['Year']) == avengers['Years since joining']:
            joined_accuracy_count += 1
    return joined_accuracy_count

EDIT: Sorry for not giving more information. The file is in pandas. So pd.read_csv('avengers')

I have two columns. 'Year' and 'Years since joining'. For example, Year would be 1963. Years since joining would be 52. I am trying to write a for-if loop to see if 2015 - 1963 = 52. And if so, add that to a count.

Error: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

You can just reference row in the loop. See the first example here: wiki.python.org/moin/ForLoop — Robert Harvey
– Robert Harvey, Commented Nov 21, 2018 at 19:40
You haven't shown how you read in the CSV. DictReader()? pandas? — roganjosh
– roganjosh, Commented Nov 21, 2018 at 19:40
If avengers['Years since joining'] is just an array of years, then row represents the current selected year for each loop iteration. So you'd just have if (2015 - row) == .... — lurker
– lurker, Commented Nov 21, 2018 at 19:41
@lurker Years since joining isn't an array of years. It's 2015 minus Years, so a two digit number. I am supposed to write a for if loop to count if this is true for all rows. — Julian
– Julian, Commented Nov 21, 2018 at 20:04
What I meant was "an array of number of years", i.e., numeric number of years. — lurker
– lurker, Commented Nov 21, 2018 at 20:52

ShlomiF · Accepted Answer · 2018-11-21 20:06:35Z

1

I think you want to use avengers.iterrows().
Basically, you're running over the values of a specific column, but that's not a "row" in the sense you want, and you have no access to other columns this way.
Try -

for _, row in avengers.iterrows():
    if (2015 - row['Year']) == row['Years since joining']:
        joined_accuracy_count += 1
return joined_accuracy_count

P.S: This is only responding to the error you had. If there are other issues with what you're trying to do and how you're going about it that's a different story.

answered Nov 21, 2018 at 20:06

ShlomiF

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3 Comments

ShlomiF Over a year ago

On a side note, the error you were getting is because avengers['Year'] and its counter-part avengers['Years since joining'] are the full columns.

Julian Over a year ago

Thanks! I think this is exactly what I'm looking for.

ShlomiF Over a year ago

Well, accepting and/or up-voting helps other users and the community as a whole ;-)

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