查找文件中一行前面的字符串的第一次出现

Question

我有一个文件格式化为：

$ORIGIN .com.rpz.my.azure_domain.com
azurebox1   CNAME   azurebox1-dr.my.azure_domain.com
$ORIGIN rpz.my.aws_domain.com
awsbox1     CNAME   awsbox1-dr.my.aws_domain.com
awsbox2     CNAME   awsbox2-dr.my.aws_domain.com
awsbox3     CNAME   awsbox3-dr.my.aws_domain.com
$ORIGIN .org.rpz.my.gc_domain.com
gcbox1      CNAME   gcbox1-dr.my.gc_domain.com
gcbox2      CNAME   gcbox1-dr.my.gc_domain.com

对于包含cname记录的每一行，我需要为其前面的$ORIGIN值追加rpz条目。因此，my.gc_domain.com CNAMES的第一列如下：

gcbox1.org.rpz.my.gc_domain.com
gcbox2.org.rpz.my.gc_domain.com

AWS看起来应该是：

awsbox1.rpz.my.aws_domain.com
awsbox2.rpz.my.aws_domain.com
awsbox3.rpz.my.aws_domain.com

我把文件读成：

f = open('current_records', 'r')
records_string = f.readlines()

如何在不捕获文件中的每个$ORIGIN行的情况下找到前面的$ORIGIN行及其rpz.*子字符串？

Answer 1

当遇到新的origin行时，我会逐行读取文件并更新变量$ORIGIN的值。

还有一些小的调整，我将通过评论相关的说明来解决。

# read the file
# use the with open scope instead of directly reading the file, so that you won't have to close the stream after.
with open("current_records") as f:  # no need for 'r' mode, it's default
    records = f.readlines()

# iterate through the list of records and their position indices
# we will need to index the list to replace a CNAME line, since strings are immutable
origin = "" # this will hold the $ORIGIN string
for n, record in enumerate(records):
    # if we encounted an $ORIGIN record, we update the variable
    if record.startswith("$ORIGIN"):
        origin = record.split()[1]
    # otherwise, we replace the CNAME value accordingly
    else:
        # build cname string
        cname = record.split()[0] + origin
        records[n] = record.replace("CNAME", cname)

# re-build the file and write it
with open("new_records", "w") as f:
    f.write("\n".join(records))  # join updated lines interposing new lines between them

这将产生一个具有相同结构和更新的CNAME‘字段’的新文件。

应该注意的是，如果不能期望文件结构完全相同，则此解决方案将无法工作。另外，您可能需要处理我在您的帖子中看不到的任何额外的空白空间。

Answer 2

import re

data = {}
with open('current_records') as f:
    for line in f:
        if line.startswith('$ORIGIN'):
            curr_type = line[8:]
            data[curr_type] = []
        else:
            data[curr_type].append(line[20:])

out = [[re.sub(r'(\w+)(.*)', r'\1', x)+key for x in value] for key, value in data.items()]
print(out)

# Output:
[['azurebox1.com.rpz.my.azure_domain.com'], ['awsbox1rpz.my.aws_domain.com', 'awsbox2rpz.my.aws_domain.com', 'awsbox3rpz.my.aws_domain.com'], ['gcbox1.org.rpz.my.gc_domain.com', 'gcbox1.org.rpz.my.gc_domain.com']]