Checking file if exist then append record
我正在创建一个具有逐行记录的日志文件。
1-如果文件不存在，则应创建文件并附加标题行和记录2-如果存在，请检查第一行中的文本
我尝试了w，a和r+；没有什么对我有用。以下是我的代码：
1 2 3 4 5 6 7 8 9 10 11 12 13 | logFile = open('Dump.log', 'r+') datalogFile = log.readline() if 'Timestamp' in datalogFile: logFile.write('%s\t%s\t%s\t%s\t '%(timestamp,logread,logwrite,log_skipped_noweight)) logFile.flush() else: logFile.write('Timestamp\t#Read\t#Write\t#e ') logFile.flush() logFile.write('%s\t%s\t%s\t%s\t '%(timestamp,logread,logwrite,log_skipped)) logFile.flush() |
如果文件不存在，则代码失败
使用
1 | logFile = open('Dump.log', 'a+') |
描述：
a+
Open for reading and writing. The file is created if it does not
exist. The stream is positioned at the end of the file. Subsequent
writes to the file will always end up at the then current
end of file, irrespective of any intervening fseek(3) or similar
以下代码可以工作：
1 2 3 4 5 | import os f = open('myfile', 'ab+') #you can use a+ if it's not binary f.seek(0, os.SEEK_SET) print f.readline() #print the first line f.close() |
检查文件是否存在会引入竞争条件，即另一个进程可以在检查返回false或true后分别创建或删除该文件，从而导致严重的错误。您应该使用：
1 2 3 4 | if open('path\to.filename', 'a+') != '': stuff_if_exists else: stuff_if_not_exists |
您正在以
1 2 3 4 5 6 7 | logFileDetails = [] with open("Dump.log","a+") as logFile: logFileDetails = logFile.readLines() if logFileDetails and"Timestamp" in logFileDetails: pass # File exists, write your stuff here else: pass # Log file doesn't exist, write timestamp here |
试试这个：
1 2 3 4 5 6 7 | import os if os.path.exists(my_file): print 'file does not exist' # some processing else: print 'file exists' # some processing |