# MicroPython¶

Access and control MicroPython internals.

## Functions¶

micropython.const(expr)

Used to declare that the expression is a constant so that the compiler can optimise it. The use of this function should be as follows:

from micropython import const
CONST_X = const(123)
CONST_Y = const(2 * CONST_X + 1)


Constants declared this way are still accessible as global variables from outside the module they are declared in. On the other hand, if a constant begins with an underscore then it is hidden, it is not available as a global variable, and does not take up any memory during execution.

micropython.opt_level([level])

If level is given then this function sets the optimisation level for subsequent 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.

micropython.mem_info([verbose])

Print information about currently used memory. If the verbose argument is given then extra information is printed.

micropython.qstr_info([verbose])

Print information about currently interned strings. If the verbose argument is given then extra information is printed.

This includes the number of interned strings and the amount of RAM they use. In verbose mode it prints out the names of all RAM-interned strings.

micropython.stack_use()

Return an integer representing the current amount of stack that is being used. The absolute value of this is not particularly useful, rather it should be used to compute differences in stack usage at different points.

micropython.heap_lock()
micropython.heap_unlock()

Lock or unlock the heap. When locked no memory allocation can occur and a MemoryError will be raised if any heap allocation is attempted.

micropython.kbd_intr(chr)

Set the character that will raise a KeyboardInterrupt exception. By default this is set to 3 during script execution, corresponding to Ctrl-C. Passing -1 to this function will disable capture of Ctrl-C, and passing 3 will restore it.

This function can be used to prevent the capturing of Ctrl-C on the incoming stream of characters that is usually used for the REPL, in case that stream is used for other purposes