如何在保留其余内容不变的情况下用信息填充空白？

Question

我正在为飞行模拟器构建场景，需要弄清楚如何编辑一个文本文件中的许多行（其中3579189行）。你知道吗

我有textclawler Pro，Node，Python SVN和Notepad++作为工具。你知道吗

原始、预编辑部分：

POLYGON_POINT -79.750000000217,42.017498354525,0
POLYGON_POINT -79.750000000217,42.016478251402,0
POLYGON_POINT -79.750598748133,42.017193264943,0
POLYGON_POINT -79.750000000217,42.017498354525,0


POLYGON_POINT -79.750000000217,42.085882815878,0
POLYGON_POINT -79.750000000217,42.082008734634,0
POLYGON_POINT -79.751045507507,42.082126409633,0
POLYGON_POINT -79.750281907508,42.083166574215,0
POLYGON_POINT -79.750781149174,42.084212672130,0
POLYGON_POINT -79.750000000217,42.085882815878,0


POLYGON_POINT -79.750000000217,42.088955814831,0
POLYGON_POINT -79.750456566883,42.087544672125,0
POLYGON_POINT -79.751642899173,42.088273325249,0
POLYGON_POINT -79.751461052298,42.088916154415,0
POLYGON_POINT -79.750000000217,42.088955814831,0

有了Notepad++的replace函数，添加POLYGON_POINT行就很容易了。现在我需要一些帮助使它看起来像这样：

BEGIN_POLYGON
POLYGON_POINT -79.750000000217,42.017498354525,0
POLYGON_POINT -79.750000000217,42.016478251402,0
POLYGON_POINT -79.750598748133,42.017193264943,0
POLYGON_POINT -79.750000000217,42.017498354525,0
END_POLY
BEGIN_POLYGON
POLYGON_POINT -79.750000000217,42.085882815878,0
POLYGON_POINT -79.750000000217,42.082008734634,0
POLYGON_POINT -79.751045507507,42.082126409633,0
POLYGON_POINT -79.750281907508,42.083166574215,0
POLYGON_POINT -79.750781149174,42.084212672130,0
POLYGON_POINT -79.750000000217,42.085882815878,0
END_POLY
BEGIN_POLYGON
POLYGON_POINT -79.750000000217,42.088955814831,0
POLYGON_POINT -79.750456566883,42.087544672125,0
POLYGON_POINT -79.751642899173,42.088273325249,0
POLYGON_POINT -79.751461052298,42.088916154415,0
POLYGON_POINT -79.750000000217,42.088955814831,0

即在每个块前面加BEGIN_POLYGON，在每个块后面加END_POLY。你知道吗

我该怎么做？你知道吗

Answer 1

使用sed的快速解决方案

cat -s file.txt |\
    sed -e 's/^$/END_POLY\nBEGIN_POLYGON/'\
    -e '1i BEGIN_POLYGON'\
    -e '$a END_POLY'

• cat -s将所有空行压缩为一行
• 第一个sed用END\u POLY和BEGIN\u POLYGON标记替换空行
• 第二个和最后一个sed将剩余的标记前置并附加到输出中

Answer 2

我将使用itertools.groupby（仅使用带有if k条件的非空组）按是否为空对行进行分组，并为每个组添加页眉/页脚。然后使用itertools.chain展平组

import itertools

with open("file.txt") as f, open("fileout.txt","w") as fw:
    fw.writelines(itertools.chain.from_iterable([["BEGIN_POLYGON\n"]+list(v)+["END_POLYGON\n"] for k,v in itertools.groupby(f,key = lambda l : bool(l.strip())) if k]))

key = lambda l : bool(l.strip()))是分组键：test for empty line but for line termination

这种方法不需要完全读取文件，因此适合于非常大的文件。它逐行处理文件，这样就不会占用内存。你知道吗