file.open无法按照我认为的方式工作

Question

My code is this:

self.data = open("/myData", "a")
self.data.close()

self.data = open ("myData", "r")


    self.master = Tk()       
    if (self.data.read()is not None):
        print 2
        print self.data.readlines()
        print 1

I usually get an empty print between the 2 and the one.

I do know for certain that there is something written in myData. I have tried other methods of opening myData, such as

self.data = open ("/myData", "r")

which gives me "permission denied" (yes, I do have reading and writing rights on that file, I checked that)

and

self.data = open ("/game-engineering/myData", "r")

which gives me "file not found".

Am I making some stupid path mistake? I do know for certain that the file is not empty, I see what is in there if I open it by hand.

Answer 1

When you call read , you "consume" the file (the cursor moves to the end of the file) - So when readlines is called it immediately hits the EOF and such returns an empty list.

In most cases (with readlines) you can just use it directly, because if the file is empty you'll get an empty list, so you'll never enter the iteration anyway.