python dict get

For an embarrassingly long time, til today, I have been wrapping my dict gets with key errors in python. I'm sure I've read it in code a bunch of times, but just brushed over why you would use get. That is until I read a bunch of PR's from my buddy Nic and notice that he never gets things with brackets and always with .get. This turns out so much cleaner to create a default case than try except.

Example

Lets consider this example for prices of supplies. Here we set a variable of prices as a dictionary of items and thier price.

prices = {'pen': 1.2, 'pencil', 0.3, 'eraser', 2.3}

Except KeyError

What I would always do is try to get the key, and if it failed on KeyError, I would set the value (paper_price in this case) to a default value.

try:
    paper_price = prices['paper']
except KeyError:
    paper_price = None

.get

What I noticed Nic does is to use get. This feels just so much cleaner that it's a one liner and feels much easier to read and understand that if there is no price for paper we set it to None.

paper_price = prices.get('paper', None)

We can just as easily set the default to other values. Let's consider sales for instance. If there is not a record for the sale of paper, it might be that we sold 0 paper in the given dataset.

paper_sales = sales.get('paper', 0)