It would be rather easy to write a program that converts ZX80 or ZX81 BASIC to OLPyBASIC since these BASICs only have one statement per line. It's relatively easy to write a program that converts from ZX Spectrum BASIC to ZX81 BASIC. Conversion programs from Microsoft BASIC e.g. CBM BASIC v2 (for e.g. C64), MBASIC, or GW-BASIC should also be possible. Also Applesoft BASIC should be possible to convert, but it has different precedence rules.
Write such a conversion program!