Writing text file with python returns odd result?

Question

Ok, I am trying to simply learn reading and writing text files in python. I can read the file etc but I get unexpected results when I attempt to write the file using write("my string") and then go to execute my code the file gets wrote to but the first line that was wrote will not fully print out. This happens in Vim with pymode and from the command line as well as interpreter. Here is the code:

#!/usr/bin/python

f = open('/Users/Desktop/data.txt', 'r+')

f.write("Test")


for lines in f:
    print lines

f.close()

Now when I execute this file to write to data.txt the output will look like this:

est <------ the "T" in Test is totally cut off. I hope this makes sense, Thanks in advance.

Does adding `f.seek(0)` before the `for` loop solve the problem? — cdhowie, Jul 25 '12 at 23:03
Also did you check the file to see if it contains "Test" or "est"? — jmetz, Jul 25 '12 at 23:04
Shouldn't you be using `a+` or `w+` for that? see http://stackoverflow.com/a/1466036/1248554 — BrtH, Jul 25 '12 at 23:07
I can't reproduce this, using your code I don't get any feedback, and adding `f.seek(0)` I get the entire file. — thomas, Jul 25 '12 at 23:08

score 3 · Accepted Answer · answered Jul 25 '12 at 23:07

I think your problem here is that you write to a file object and then immediately read back from it.

Try adding the line

f.seek(0)

after you write to the file but before you read from it. This repositions where in the file Python is looking to the beginning.

Writing text file with python returns odd result?

1 Answers1