Ask a function return value display problem

First, you define the function, you don't call it

Second, your file open mode is set to r+, after writing the contents, the pointer is at the end of the file, you need f.sek(0), to put the pointer back

r+ mode can be both read and write, I have written content on the file, but run the program print does not come out

First, the problem with the first picture. You don't run the function

After writing, the pointer to the file stays at the end by default. To read the contents, you can adjust the pointer to the start position