[BUG] Defining 'Ws' or 'Gs' in custom circuits fails about impedance.py HOT 5 CLOSED

The easiest solution seems to be renaming Gs and Ws, but the issue really stems from how p_string is constructed in:

def extract_circuit_elements(circuit):
    extracted_elements = []
    p_string = [x for x in circuit if x not in 'ps(),-/']

from impedance.py.

Ah, so it's because we've used s to dictate series...

I think there's an elegant way to do this with regular expressions rather than just ignoring characters, but I haven't played around with it much.

from impedance.py.

@BGerwe I think we should just be able to remove s (since it's never in a circuit string, we use -) and / (since we don't us it anymore) from the line you pasted above?

from impedance.py.

That seems to work! Something else I noticed during this, the way elements with >1 parameters is a little confusing now. Ex:

Initial guesses:
    R_0 = 1.00e+01 [Ohm]
  G_1_0 = 1.00e+02 [Ohm]
  G_1_1 = 1.00e-01 [sec]
    W_1 = 5.00e+01 [Ohm sec^-1/2]

But we could have it print as

Initial guesses:
    R_0 = 1.00e+01 [Ohm]
  G_1_p[0] = 1.00e+02 [Ohm]
  G_1_p[1] = 1.00e-01 [sec]
    W_1 = 5.00e+01 [Ohm sec^-1/2]

without changing much. Are you fine with including that in this issue/PR? This acts funny when you define constants so I won't worry about it.

from impedance.py.

Yeah, I think the double underline is a bit ugly haha. Maybe it’d be nice to have it be something like latex (I.e. Gs_{1,1}).

This does affect a few things though so probably best for a new PR.

from impedance.py.