如何两次附加到列表？ [英] how to append to a list twice?
问题描述
如果我想创建一个表单[100,99,99,98,98,97,97 ...]
（其中每个项目在第一个项目后重复两次） ），我怎么能最有效地做？
？
现在我有这个：
series = [100]
for x in range（10）：＃just for testing
series.append（series [-1] - 1）
>
但当然只有一次，而且我不想复制
并粘贴追加线。也许有比这更好的方法。
谢谢。
If I want to create a list of the form [100, 99, 99, 98, 98, 97, 97...]
(where each item is repeated twice after the first one), how might I do
that most efficiently?
Right now I have this:
series = [100]
for x in range(10): # just for testing
series.append(series[-1] - 1)
But of course that only does it once, and I don''t want to have to copy
and paste the append line. Perhaps there''s a better way than this.
Thanks.
推荐答案
" John Salerno" <乔****** @ NOSPAMgmail.com>在留言中写道
news：ui ****************** @ news.tufts.edu ...
"John Salerno" <jo******@NOSPAMgmail.com> wrote in message
news:ui******************@news.tufts.edu...
如果我想创建一个表单[100,99,99,98,98,97,97 ......]
（其中每个项目在第一个项目后重复两次），我该怎么办？最有效的？
现在我有这个：
series = [100]
对于范围内的x（10）：＃just for testing
series.append（series [-1] - 1）
但当然只做了一次，我不想复制
并粘贴追加线。也许还有比这更好的方法。
谢谢。
If I want to create a list of the form [100, 99, 99, 98, 98, 97, 97...]
(where each item is repeated twice after the first one), how might I do
that most efficiently?
Right now I have this:
series = [100]
for x in range(10): # just for testing
series.append(series[-1] - 1)
But of course that only does it once, and I don''t want to have to copy
and paste the append line. Perhaps there''s a better way than this.
Thanks.
series = [100]
for x在范围（10）中：＃仅用于测试
series.extend（[series [-1] - 1] * 2）
series = [100]
for x in range(10): # just for testing
series.extend([series[-1] - 1]*2)
John Salerno写道：
John Salerno wrote:
如果我想创建一个表单[100,99,99,98,98,97,97 ...]的列表/>（每个项目在第一个项目后重复两次），我怎么做才能最有效？
现在我有这个：
系列= [100]
对于范围内的x（10）：＃仅用于测试
series.append（series [-1] - 1）
但当然只有它曾经，我不想复制
并粘贴追加线。也许还有比这更好的方法。
谢谢。
If I want to create a list of the form [100, 99, 99, 98, 98, 97, 97...]
(where each item is repeated twice after the first one), how might I do
that most efficiently?
Right now I have this:
series = [100]
for x in range(10): # just for testing
series.append(series[-1] - 1)
But of course that only does it once, and I don''t want to have to copy
and paste the append line. Perhaps there''s a better way than this.
Thanks.
series = [100]
for i in range（1,10）：
series.extend（[100-i] * 2）
print series
[100,99,99,98,98,97,97,96,96,95,95,94,94,93,93,92,92，
91,91]
Gerard
series = [100]
for i in range(1,10):
series.extend([100-i]*2)
print series
[100, 99, 99, 98, 98, 97, 97, 96, 96, 95, 95, 94, 94, 93, 93, 92, 92,
91, 91]
Gerard
John Salerno< jo ****** @ NOSPAMgmail.com>写道：
John Salerno <jo******@NOSPAMgmail.com> wrote:
如果我想创建一个表单列表[100,99,99,98,98,97,97 ...]
（每个项目的位置）在第一个之后重复两次），我怎么能最有效地做？
现在我有这个：
series = [100]
for x in range（10）：＃just for testing
series.append（series [-1] - 1）
但当然只有一次，我不喜欢我不想复制
并粘贴追加线。也许还有比这更好的方法。
If I want to create a list of the form [100, 99, 99, 98, 98, 97, 97...]
(where each item is repeated twice after the first one), how might I do
that most efficiently?
Right now I have this:
series = [100]
for x in range(10): # just for testing
series.append(series[-1] - 1)
But of course that only does it once, and I don''t want to have to copy
and paste the append line. Perhaps there''s a better way than this.
def makeseries（N）：
series = [N]
append = series.append
for the tailer in xrange（N-1，-1，-1）：
append（tailer）
追加（tailer）
返回系列
series = makeseries（100）
假设通过&最有效的你的意思是最快，这可能会来
关闭;你也想要另外一个替代方案，其中makeseries是一个
生成器，只生成值，最后一个赋值变为
series = list（makeseries（100） ）。
Alex
def makeseries(N):
series = [N]
append = series.append
for tailer in xrange(N-1, -1, -1):
append(tailer)
append(tailer)
return series
series = makeseries(100)
assuming that by "most efficiently" you mean "fastest", this might come
close; you''ll want to also time an alternative where makeseries is a
generator which just yields the values, and the last assignment becomes
series=list(makeseries(100)).
Alex
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