处理来自多个驱动器的项列表

Question

我有一个元组列表，如下图所示。我将列表传递给一个python函数来处理列表中的每一项。我需要访问多个系统驱动器来处理列表。我当前的程序每次都会打开驱动器。这是低效的。只有当列表中的当前项与处理的最后项来自不同的驱动器时，我才想打开驱动器。

(1, 18911232, 'af1a83d6b18bf3e065be82cf44246037', 'D')
(2, 18911744, 'd5cedca078545cbcb0b2a9b514f9b92d', 'D')
(3, 18912256, '457ee2f5dc6f95b09599fc3f479878b6', 'D')
(4, 27076608, '8fb1ee8d6d8df00e53055e0eb48ef2e5', 'E')
(5, 27077120, 'a9ea5ccfebe4d6b3ecdd429518fff688', 'E')
(6, 27077632, 'ff722e8bb3c731ece625f882a090f100', 'E')
(7, 19604324352, 'd1fd613c04c983d73d79027f2a3425f9', 'C')
(8, 19604324864, '6f51f480b2ad733f20a54c8d3f5dd38c', 'C')
(9, 19604325376, '066fdaddf301b83402934e5783a3eec3', 'C')

def check(oldList):
newList = []#To hold processed list
try:
for item in oldList:
drive = item[3]
volume = r"\." + '\'+ drive + ':' #Constructing string to open the drive.                  
with open(volume, 'rb') as disk: #Open drive
disk.seek(item[2])#Move to sector address on disk
sector_data = disk.read(512) #Read sector data (512 bytes)
sectorHash = md5HashFunc(sector_data)#Hash sector data
if sectorHash==item[3]:  
pass #If data matches, do nothing - sector still intact
else:
newList.append(item[1])
except Exception as err:
logging.exception(err)
logging.info('=======================================================n')
notificationMessage('An error occured and has been logged, see log for details.')
return newList #Return new list.

Answer 1

仅当列表中的当前项与最后处理的项来自不同的驱动器时才希望打开驱动器

存储最后一次看到的驱动器，然后检查它是否在循环

时更改例如

drive = None
prevDrive = None
disk = None
for item in oldList:
drive = item[3]
if drive != prevDrive
volume = r"\." + '\'+ drive + ':'
if disk is not None:  # if previously assigned
disk.close()
disk = open(volume, 'rb')

# do work
disk.seek(item[2])
prevDrive = drive
if disk is not None:
disk.close()

这只适用于一个相对有序的驱动器列表。

另一种方法是存储一个文件句柄字典

drive_map = {item[3]: open(r"\." + '\'+ item[3] + ':', 'rb') for item in oldList}
for item in oldList:
disk = drive_map[item[3]]
# do work
disk.seek(item[2])

# make sure to close all the files when done
for _, f in drive_map.items():
f.close()

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也不确定为什么要检查扇区哈希等于驱动器值，因为哈希通常不是单个字符