A pythonic way to sum the values of a dict with a specified key list?

Question

Let's say I have a list (or other iterable object) ['a','b','c','d'] . I have a dict X . I can sum them up in the naive way:

s = 0
for k in ['a','b','c','d']:
    s += X[k]

But is there a more pythonic way?

Answer 1

你可以做：

s = sum(X[k] for k in ['a','b','c','d'])

Answer 2

Yes, by using the sum function and a generator expression . You can even iterate over the characters of a string:

s = sum(X[k] for k in 'abcd')