是否可以将此代码片段转换为列表理解？如何？
a = 0
b = {'a': [(1, 'a'), (2, 'b'), (3, 'c')], 'b': [(4, 'd'), (5, 'e')]}
for c, d in b.iteritems():
for e, f in d:
a += e
// now a = 15
尝试了几种方法。我想知道一种方法（如果可能的话）通过列表理解来简化这个总和：
a = sum(...)
提前谢谢您， pf.me
a = 0
b = {'a': [(1, 'a'), (2, 'b'), (3, 'c')], 'b': [(4, 'd'), (5, 'e')]}
for c, d in b.iteritems():
for e, f in d:
a += e
// now a = 15
Tried several ways. I want to know a way (if possible) to simplify this sum with a list comprehension:
a = sum(...)
Thank you in advance,
pf.me
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a = sum(e for d in b.itervalues() for e, _ in d)适用于 Python 2.7。a = sum([e for d in b.itervalues() for e, _ in d])适用于 Python 2.3。我还没有尝试过，但是
a = sum(e for d in b.values() for e, _ in d)应该是 Python 3.0 的等效项。a = sum(e for d in b.itervalues() for e, _ in d)works in Python 2.7.a = sum([e for d in b.itervalues() for e, _ in d])works in Python 2.3.I haven't tried it, but
a = sum(e for d in b.values() for e, _ in d)should be the Python 3.0 equivalent.sum(j for _,i in b.iteritems() for j,_ in i)就可以了。sum(j for _,i in b.iteritems() for j,_ in i)will do it.