如何使用startswith函数生成类似于diff工具中的输出？

Question

请帮我解决(我认为很有趣)算法问题。我今天花了一整天来解决这个问题。这是我的代码：

rman_config = ('''CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
''')

rman_new_parameters = [('RETENTION POLICY', 'TO RECOVERY WINDOW OF 2 DAYS'),
                       ('CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE', 'DISK TO controlfile_%F'),
                       ('CONTROLFILE AUTOBACKUP', 'ON'),
                       ('DEVICE TYPE', 'DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET')]

tuple_to_search = tuple([i[0] for i in rman_new_parameters])

for line in rman_config.splitlines():
    if line.startswith(tuple_to_search, 10):
        print('-  ' + line)
        print('+  CONFIGURE ' + '[parameter] ' + '[new value]' + ';')
    else:
        print('   ' + line)

其中：

• rman_config -具有默认配置的变量
• rman_new_parameters -新参数按随机顺序覆盖默认值：
  • 元组中的第一个元素是一个参数(即CONTROLFILE AUTOBACKUP)。
  • 元组中的第二个元素是一个新值(即ON)。

​

到目前为止，我有这样的输出：

-  CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
+  CONFIGURE [parameter] [new value];
   CONFIGURE BACKUP OPTIMIZATION OFF; # default
   CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
-  CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
+  CONFIGURE [parameter] [new value];
-  CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
+  CONFIGURE [parameter] [new value];
-  CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
+  CONFIGURE [parameter] [new value];
   CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default

但是我想要这个(就像在Diff中)：

-  CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
+  CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 2 DAYS;
   CONFIGURE BACKUP OPTIMIZATION OFF; # default
   CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
-  CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
+  CONFIGURE CONTROLFILE AUTOBACKUP ON;
-  CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
+  CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO cf_%F;
-  CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
+  CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET;
   CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default 

startswith函数很好，但它不告诉我识别哪个元组(只返回真假)。我使用上面的代码的问题是如何映射下一行：

if line.startswith(tuple_to_search, 10):

如果它是真到rman_new_parameters 列表.

我不知道怎么解决这个问题？我会非常感谢你的帮助。

Answer 1

for line in rman_config.splitlines():
    for params in rman_new_parameters:
        if line.startswith(params[0], 10):
            print('-  {}'.format(line))
            print('+  CONFIGURE {} {}'.format(*params))
            break
    else:
        print('   {}'.format(line))

基本上，我没有将元组传递给.startswith，只是在一个循环中逐个测试。

还有，else。

Answer 2

我不知道你想做什么。但不管怎样，我写的代码。看看这个答案是否符合你的问题。主要区别在于您的if-else块变成了try-except块。重点是index函数，它返回参数在tuple_to_search中第一次出现的位置。我假设rman_new_parameters中所有参数的值都与rman_config不同。

rman_config = ('''CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
''')

rman_new_parameters = [('RETENTION POLICY', 'TO RECOVERY WINDOW OF 2 DAYS'),
                       ('CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE', 'DISK TO controlfile_%F'),
                       ('CONTROLFILE AUTOBACKUP', 'ON'),
                       ('DEVICE TYPE', 'DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET')]

tuple_to_search = [i[0] for i in rman_new_parameters]

for line in rman_config.splitlines():
    try:
        index = [line.startswith(tup, 10) for tup in tuple_to_search].index(True)
        print('-  ' + line)
        print('+  CONFIGURE ' + " ".join(rman_new_parameters[index]) + ';')
        #Add these if you don't need to check parameter once matched.
        #del rman_new_parameters[index]
        #del tuple_to_search[index]
    except:
        print('   ' + line)

产出：

-  CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
+  CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 2 DAYS;
   CONFIGURE BACKUP OPTIMIZATION OFF; # default
   CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
-  CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
+  CONFIGURE CONTROLFILE AUTOBACKUP ON;
-  CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
+  CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO controlfile_%F;
-  CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
+  CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET;
   CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default

P.S.

我的输出与您想要的输出略有不同(2行不同)。我也不知道原因。因此，请确保这是您想要的输出。

你的：

...
+  CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO cf_%F;
...
   CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default 

我的：

...
+  CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO controlfile_%F;
...
   CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
                                                                        ^
                                                                    no space here