About this below Code

Question

Language:Python

msg = "Hello world!"
file = open("newfile.txt", "w")
amount_written = file.write(msg)
print(amount_written)
file.close()

Output:
12

I have a doubt here
1)Why does it print length of the string rather than printing "Hello World! "?
2)Why do we have to use another varaible "amount_written" here if we run the code like this

msg = "Hello world!"
file = open("newfile.txt", "w+")
file.write(msg)
print(file.read())
file.close()

Output:
No output

Can anyone please Explain this ?
Thank you

Answer 1

Even that will print the length

Answer 2

But its "W+" it means write and read why do i need to close it again

Answer 3

But without using len how does the program show "12" as output