Getting the first non None value from list

Question

Given a list, is there a way to get the first non-None value? And, if so, what would be the pythonic way to do so?

For example, I have:

• a = objA.addr

Answer 1

When the items in your list are expensive to calculate such as in

first_non_null = next((calculate(x) for x in my_list if calculate(x)), None)

# or, when receiving possibly None-values from a dictionary for each list item:

first_non_null = next((my_dict[x] for x in my_list if my_dict.get(x)), None)

then you might want to avoid the repetitive calculation and simplify to:

first_non_null = next(filter(bool, map(calculate, my_list)), None)

# or:

first_non_null = next(filter(bool, map(my_dict, my_list)), None)

Thanks to the usage of a generator expression, the calculations are only executed for the first items until a truthy value is generated.