CODEWITHSUNDEEP
pythonfile-io
stj242
stj242

Reputation: 43

Writing time difference to file

I am trying to write a log file that logs time differences between executions of a loop. I am very new to Python and it seems I can't quite make it work.

This is the loop:

def writeData(self):
    f = open('logfile','w')
    timeInMs = 0
    while True:
        lastTimeInMs = timeInMs
        timeInMs = long(round(time.time() * 1000))
        timeDifference = timeInMs - lastTimeInMs
        print(timeDifference) #write to console
        f.write(str(timeDifference) + "\n") #write to logfile
        doc = {'foo': 'bar'}
        self.db.save(doc)

It prints the timeDifference just fine to the console, but the logfile remains empty. However, writing to the logfile works just fine if I use absolute times!

f.write(str(timeInMs) + "\n")

Can somebody please tell me why that is and how I can fix this problem? I would have expected print and write to behave the same way. Thanks!

Upvotes: 0

Views: 85

Answers (2)

Dan D.
Dan D.

Reputation: 74675

If you expect the output to appear in the file directly after the f.write() call, you have to call f.flush() after the call to f.write().

Although f.close() was suggested, it is not the solution to the problem. f.close() effectively calls f.flush() before closing the file; however, that would be too late, so to get the written data to appear in the file without closing it use f.flush().

Upvotes: 2

llrs
llrs

Reputation: 3397

I am not sure how the writ functions deals with these expression: f.write(str(timeDifference) + "\n") Why don't you change to 

timeDifference = str(timeDifference)+"\n"
f.write(timeDifference)

As Khelwood pointed in comments don't forget to close the open file with a f.close() at the end of the function outside the while-loop

Upvotes: 0

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