python 字符串格式 : way to not use two lists?

Question

使用以下代码:

a = ['foo', 'bar', 'doh', 'rae']

我想要字符串 SUM(foo) AS foo, SUM(bar) AS bar, SUM(doh) AS doh, SUM(rae) AS rae。这有效:

尝试了一些聪明的东西，比如 'SUM(%s) AS %s' % ([x for x in a], [x for x in a]) 但显然它没有用，并且使用两个列表推导式感觉效率极低。

有什么建议吗？

Answer 1

为什么不使用 str.format method ？

", ".join(['SUM({n}) AS {n}'.format(n=x) for x in a])
# Returns SUM(foo) AS foo, SUM(bar) AS bar, SUM(doh) AS doh, SUM(rae) AS rae

如果 a 是一个大列表，您可能想改用生成器，以避免首先在内存中创建整个列表，正如 GWW 指出的那样。

", ".join('SUM({n}) AS {n}'.format(n=x) for x in a)