seek. function without output

Question

 tips_file = open('code_tips.txt', 'w+')
 tips_file.write('-use simple function and variable names\n-comment code\n-organize code into functions\n')
 tips_file.seek(0)
 tips_text = tips_file.read()
 print (tips_text)

There is no output for the above code. But for the following codes, there is output

tips_file.seek(13)
tips_text = tips_file.read()
print(tips_text)

I am wondering why there is difference

I just figure out that if I separate the code into 2 cells

tips_file = open('code_tips.txt', 'w+')
tips_file.write('-use simple function and variable names\n-
commentcode\n-organize code into functions\n')

and

tips_file.seek(0)
tips_text = tips_file.read()
print(tips_text)

Then I can deliver output if I run the first cell once and the second cell twice. If only run the second cell for once, it gives no output as the same of the problem. I am really confused.