Question

I am parsing JSON requests using the JSON library which parses into python dictionary. As the requests are user-generated, I need to fix default values for parameters that have not been supplied. Other languages have stuff like ternary operators which make sense for repetitive applications. But the code below needs 4 lines per parameter.

if "search_term" in request.keys():
    search_term=request['search_term']
else:
    search_term=""
if "start" in request.keys():
    start=request['start']
else:
    start=0
if "rows" in request.keys():
    rows=request['rows']
else:
    rows=1000000

Is there a Pythonic way to reduce the lines of code or make it more readable?

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Edit: Both the (top) answers are equally useful. I used both in different circumstances

Answer 1

Use the dict.update method on a copy of the defaults:

defaults = dict(a=1, b=2, c=3)

result = dict(defaults)  # Copy the defaults
result.update(request)  # Update with your values

This allows you to keep defaults as a class attribute or module global variable, which you probably want to do.

You can also combine the last two lines into:

result = dict(defaults, **request)

For another solution, see Kevin’s answer.