nb_to_py.pl

#!/usr/bin/env perl

# define the mapping from Mathematica vars to python vars
$r1 = "MIX_RATE";
$r2 = "FADE_RATE";
$s = "SCALE";
$u1 = "last_signal";
$u2 = "NOISE_FLOOR";
$y = "ss_old";
$v = "v_old";

# loop through every line on stdin
while (<>) {
    s/[^!-~\s]//g;      # strip non-ascii characters
    s/{{x\[t\]->//g;    # remove beginning {{x[t]->
    s/}}//g;            # remove ending }}
    s/\+\n/\+/g;        # add line breaks at ever + or -
    s/\-\n/\-/g;
    s/Box//g;           # Mathematica sometimes adds 'Box' 
                        # I don't know why

    # replace r_1 with python var
    s/Subscript\[r, 1\]/$r1/g;

    # replace r_1^x with python's r1**x
    s/Subsuperscript\[r, 1, ([0-9]+)\]/$r1**$1/g;
    
    # repeat for r_2, u_1, and u_2
    s/Subscript\[r, 2\]/$r2/g;
    s/Subsuperscript\[r, 2, ([0-9]+)\]/$r2**$1/g;
    s/Subscript\[u, 1\]/$u1/g;
    s/Subsuperscript\[u, 1, ([0-9]+)\]/$u1**$1/g;
    s/Subscript\[u, 2\]/$u2/g;
    s/Subsuperscript\[u, 2, ([0-9]+)\]/$u2**$1/g;

    # replace E^( with np.exp(
    s/E\^\(/np.exp(/g;
    # replace E^x with np.exp(x)
    s/E\^([0-9a-z]+)/np.exp($1)/g;

    # replace ^x with **x
    s/\^([0-9a-z]+)/**$1/g;

    # replace integer x/y with x.0/y so that python does float division
    s/([0-9]+)\/([0-9]+)/($1.0\/$2)/g;

    # replace whitespace with * (for multiplication)
    s/([a-z0-9)])\s+(?=[a-z0-9(])/$1 * /ig;

    # put a space around - and +
    s/([^(])-/$1 - /g;
    s/(.)\+(.)/$1 + $2/g;

    # put ever instance of np.exp on a new line.
    # this is totally for aesthetics and specific to my use
    s/([-+] [^-+n]*(?:np.exp\([^\)]*\)[^-+])?)/\\\n$1/g;

    # replace s, y and v in Mathematica with python vars
    # assert that s, v, and y are surrounded by word boundaries
    s/\bs\b/$s/g;
    s/\by\b/$y/g;
    s/\bv\b/$v/g;

    print; 
    }