Why I can't read any character in this Python code

Question

I know, w+ means both read and write, then I write this code to read some message from a txt file and write some message into it

This is my code:

f = open('test', 'w+')
f.write('yes yes yes\n')
print f.read()
......
f.close()

when i run it, It only print newline, and didn't print yes yes yes

then I open test file, I found yes yes yeswas in it!

Why it' just print new line, but print yes, and what's the difference between w+ & r+

Answer 1

You should put cursor at the beginning of file before reading.

f.seek(0)
f.read()