在 Python 的现代版本中，我建议 SilentGhost 发布的内容(为了清楚起见在此重复):

sum(i for i, j in list_of_pairs)

在此答案的早期版本中，我曾建议这样做，这是必要的，因为 SilentGhost 的版本在当时最新的 Python (2.3) 版本中不起作用:

sum([pair[0] for list_of_pairs])

现在那个版本的 Python 已经过时了，而且 SilentGhost 的代码适用于所有当前维护的 Python 版本，所以不再有任何理由推荐我最初发布的版本.

I have a list of tuples (always pairs) like this:

[(0, 1), (2, 3), (5, 7), (2, 1)]

I'd like to find the sum of the first items in each pair, i.e.:

0 + 2 + 5 + 2

How can I do this in Python? At the moment I'm iterating through the list:

sum = 0
for pair in list_of_pairs:
   sum += pair[0]

I have a feeling there must be a more Pythonic way.

In modern versions of Python I'd suggest what SilentGhost posted (repeating here for clarity):

sum(i for i, j in list_of_pairs)

In an earlier version of this answer I had suggested this, which was necessary because SilentGhost's version didn't work in the version of Python (2.3) that was current at the time:

sum([pair[0] for pair in list_of_pairs])

Now that version of Python is beyond obsolete, and SilentGhost's code works in all currently-maintained versions of Python, so there's no longer any reason to recommend the version I had originally posted.