docs/library/micropython: Describe optimisation levels for opt_level().
@@ -33,6 +33,18 @@ Functions
compilation of scripts, and returns ``None``. Otherwise it returns the current
optimisation level.
+ The optimisation level controls the following compilation features:
+
+ - Assertions: at level 0 assertion statements are enabled and compiled into the
+ bytecode; at levels 1 and higher assertions are not compiled.
+ - Built-in ``__debug__`` variable: at level 0 this variable expands to ``True``;
+ at levels 1 and higher it expands to ``False``.
+ - Source-code line numbers: at levels 0, 1 and 2 source-code line number are
+ stored along with the bytecode so that exceptions can report the line number
+ they occurred at; at levels 3 and higher line numbers are not stored.
+
+ The default optimisation level is usually level 0.
+
.. function:: alloc_emergency_exception_buf(size)
Allocate *size* bytes of RAM for the emergency exception buffer (a good
