如何检查txt文件中所有行的前5个字符是否为特定单词？

Question

我用python来做一个简单的信息检索程序，它获取一个clientID和一个用户的客户机id是txt文件中每一行的前5个字符

RYMAU
ELOWE
RUKUM
KLKID
LAJON

我想让一个用户输入一个5个字母的id，并检查每一行中的一个特定的客户机id，此时我已经想到了这个：

^{pr2}$

但这只检查第一行的前5个字母，而不是全部。在

文本文件的实际外观如下：

NeQua,High,Running,5,Swimming,40,Aerobics,40,Football,20,Tennis,10
ImKol,Moderate,Walking,40,Hiking,0,Cleaning,40,Skateboarding,30,Basketball,20
YoTri,Moderate,Walking,20,Hiking,30,Cleaning,40,Skateboarding,20,Basketball,40
RoDen,High,Running,20,Swimming,20,Aerobics,40,Football,30,Tennis,50
NaThe,Moderate,Walking,30,Hiking,30,Cleaning,20,Skateboarding,10,Basketball,30
ReWes,Moderate,Walking,30,Hiking,20,Cleaning,50,Skateboarding,40,Basketball,20
BrFre,High,Running,20,Swimming,30,Aerobics,30,Football,30,Tennis,20
KaDat,High,Running,30,Swimming,20,Aerobics,10,Football,20,Tennis,30
ViRil,High,Running,50,Swimming,50,Aerobics,60,Football,40,Tennis,50
TrGeo,High,Running,10,Swimming,20,Aerobics,30,Football,30,Tennis,20
DaWay,High,Running,60,Swimming,50,Aerobics,40,Football,50,Tennis,50
CaAma,High,Running,30,Swimming,20,Aerobics,10,Football,20,Tennis,30
ArRes,High,Running,0,Swimming,10,Aerobics,30,Football,20,Tennis,20
BeVic,High,Running,20,Swimming,20,Aerobics,30,Football,30,Tennis,10
MaFre,High,Running,10,Swimming,20,Aerobics,20,Football,40,Tennis,30
AnMer,Moderate,Walking,40,Hiking,30,Cleaning,30,Skateboarding,20,Basketball,30
SaBro,Moderate,Walking,30,Hiking,20,Cleaning,30,Skateboarding,20,Basketball,20
PoLig,Moderate,Walking,20,Hiking,20,Cleaning,20,Skateboarding,30,Basketball,30
HeZbe,Moderate,Walking,30,Hiking,40,Cleaning,20,Skateboarding,40,Basketball,10
GiLop,Moderate,Walking,40,Hiking,0,Cleaning,30,Skateboarding,40,Basketball,20
DeTur,Moderate,Walking,10,Hiking,0,Cleaning,10,Skateboarding,30,Basketball,30
LaKin,Moderate,Walking,20,Hiking,20,Cleaning,30,Skateboarding,30,Basketball,20
AnVen,Moderate,Walking,50,Hiking,0,Cleaning,50,Skateboarding,50,Basketball,20
LoLew,Moderate,Walking,10,Hiking,20,Cleaning,10,Skateboarding,30,Basketball,40
NyRed,Moderate,Walking,0,Hiking,0,Cleaning,0,Skateboarding,0,Basketball,20

Answer 1

您需要阅读所有行，并测试每行的前五个字符：

with open('clientRecords.txt') as fob:
    allowed_access = any(line.startswith(clientID) for line in fob)
if allowed_access:
    print('Access granted')
else:
    print('Access denied')

如果文件中有任何一行以提供的前缀开头，则allowed_access将为{}，并且一旦发现命中，它将立即停止检查行。在

注意：为了避免作弊，您可能需要验证所提供的clientID实际上有五个字符长。在

如果要获取与该ID关联的行，而不仅仅是该ID是否存在，可以将该检查修改为：

^{pr2}$

另外，如果您经常执行这个测试，并且记录文件很少更改，那么您可能需要在内存中缓存以减少I/O工作。您将预先加载一次有效的ID（而不是在任何验证用户的循环或事件处理程序中）：

with open('clientRecords.txt') as fob:
    known_users = {line[:5] for line in fob}

然后，每次登录测试简化为：

if clientID in known_users:
    print('Access granted')
else:
    print('Access denied')

它将立即运行（出于所有意图和目的），而不是在每次测试中重新打开和重新读取文件的代价。您可能需要一个过时超时，之后每隔一段时间重新缓存known_users，或者os.stat文件，如果文件被修改，则重新缓存。在

获取关联行的版本是：

with open('clientRecords.txt') as fob:
    known_users = {line[:5]: line for line in fob}

检查/查找：

access_data = known_users.get(clientID)  # Returns None if the clientID is not found, or the complete line if it is found
if access_data is not None:
    print('Access granted')
else:
    print('Access denied')