file handling Newbee question

[middlecope]

I am a pascal programmer learning python
Raspberry pi 2, python 3.9

f = open("temps.txt")
f.write("attemt1\r\n")
f.close

Nothing is written to the file. When I add the next lines to the script

f = open("temps.txt","r")

Now there is a new line in the file
What do I do wrong?
Thanks for your attention. Teunis