python readline() output nothing

Question

I got nothing back from the command readline(). I am new to python and totally confused now.

my_file = open("test.txt", "w+")
my_file.write("This is a test")
print my_file.readline()

we'll need a bit more of your code in order to understand the problem you're having — Aaron, Aug 01 '16 at 16:46
In order to read the line you'd have to open the file in read mode. — mechanical_meat, Aug 01 '16 at 16:47
Don't post images of code. They're harder to read, copy and search for. — Vincent Savard, Aug 01 '16 at 16:47

score 5 · Answer 1 · answered Aug 01 '16 at 16:50

When you write to a file, you overwrite any previous contents of the file and leave the pointer at the end of the file. Any attempt to read after that will fail, since you're already at the end of the file.

To reset to the beginning of the file and read what you just wrote, use:

my_file.seek(0)

score 0 · Answer 2 · answered Aug 01 '16 at 16:54

Because after you wrote content in you file. the cursor is at the end of the file. Before you use readline(), use my_file.seek(0) first, If your file content is only This is a test, you can get your want. Deep into this, please go to : https://docs.python.org/2.7/tutorial/inputoutput.html#reading-and-writing-files

python readline() output nothing

2 Answers2