Python update a key in dict if it doesn't exist

Question

I want to insert a key-value pair into dict if key not in dict.keys(). Basically I could do it with:

if key not in d.keys():
    d[key] = value

Answer 1

You do not need to call d.keys(), so

if key not in d:
    d[key] = value

is enough. There is no clearer, more readable method.

You could update again with dict.get(), which would return an existing value if the key is already present:

d[key] = d.get(key, value)

but I strongly recommend against this; this is code golfing, hindering maintenance and readability.