how to write data into a file inside the subscriber callback function?

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Hi everyone, I am pretty new in learning Python and ROS and I have a little problem. I am publishing an input function into a topic and a subscriber reads the needed data and computes the convolution in real-time to get the response of the linear system of the matter. this callback function works at 50 Hz. I wrote this into the callback function in order to save a specific response value for each time step.

f = open("response.txt", "a")
f.write("\n")
f.close()

the problem is pretty trivial. it does not create any file in that directory and in any other as well. could you give me a feedback about this? Thank you in advance