Python Forum

Hi Group, I'm new. So hopefully I'll figure out how to navigate this forum and get the help I need as I'm trying to learn python. Currently, I'm having a problem with what I believe is called f-string concatenation. I'm using pycharm to code python as I'm working my way through a book called Neural Networks from Scratch. The code I've typed out is long.... but the snippet I'm having a problem with is this:

print(f'epoch:{epoch}, ' +
                 f"acc: {accuracy: .3f}, ' +
                 f'loss: {loss: .3f}, ' +
                 f'lr: {optimizer.current_learning_rate}')

The error is:

Error:
Traceback (most recent call last):
  File "C:\Users\........", line 465, in <module>
    f'loss: {loss: .3f}, ' +
TypeError: unsupported format string passed to NoneType.__format__

I think that pycharm perhaps doesn't like the way it's set up. I don't know. Can someone explain what's gone wrong or how I can fix it?

TIA.

It's telling you that instead of being a number as you suppose, one of your variables (probably loss) is None. Trying to apply a numeric format to None generates an error.

Actually, I think I understand now. It wasn't apparent at first.

Thanks.

Actually your code shows that you don't understand f-strings. There is no need of concatenation.

print(f'epoch:{epoch}, acc: {accuracy: .3f}, loss: {loss: .3f}, lr: {optimizer.current_learning_rate}')

This is assuming you fix the problem with loss being None.