Question: I have a .csv file that has 25 columns. In this data, column 18 is a People\_ID, and column 19 is a Donation Date. I have pre-sorted the data using Linux so that all People ID's appear together, sorted by donation date in descending order.

Here is where I'm not sure how to proceed. I need to find all lines that have the same People\_ID and Donation Date, sum various values, and then output a single line into the output. So essentially, every line in the file would be either a different customer, or a different donation date by the same customer. Would it be best to use a dictionary using the People\_ID as the key? How would this look syntactically?

I was thinking something like this:

```
with open("file.csv") as csv_file:
for row in csv.reader(csv_file, delimiter=','):
    if row[18] in data_dict:
        # something something

```

Answer: 
I feel stupid. I just realised that it's part of logback and not part of play. You can define your own variables like thus:

```
<property name="USER_HOME" value="/home/sebastien" />

```

Checkout link here for more details:
<http://logback.qos.ch/manual/configuration.html#definingProps>
appliation.home is defined by play framework itself.

<https://github.com/playframework/playframework/blob/2.4.x/framework/src/play/src/main/scala/play/api/Logger.scala#L199>

You must have another problem.