OPT-13 Pre-load functions for binary operations to known types


CPython will compile complex mathematical operations into opcodes based on operator precedence and stack. All binary operations and inplace operations (Add, subtract, divide, floor divide, power), take 2 arguments, the left and right hand objects.


c = a + b

In this example, the value of a and b is loaded (from LOAD_FAST, LOAD_NAME, or LOAD_GLOBAL depending on the scoping) and the reference count is incremented. The binary add operation then calculates a new value and decrements the reference to a and b.

The API for working out the correct magic-method to call is in CPython’s abstract API.

For example, the + operator will call PyNumber_Add(a, b).

This will resolve to:

  1. IF b is a subtype of a and it implements that slot, use that

  2. If a has that slot implemented, use that

  3. If b has that slot implemented, use that

For each of these, the call can return a singleton string, Py_NotImplemented.

There is also another branch for inplace operators, where if the inplace slot is not implemented, it will fall back to the regular slot.


If the left-hand and right-hand operands are both known types at compile-time, Pyjion will work out the logic of which slot has preference at compile time and emit a method call to the implementation of that slot.


  • Add binary operations where left and right are known types are faster.


  • None

Further Enhancements

  • Determine more types through profiling.


This optimization is enabled at level 1 by default. See Optimizations for help on changing runtime optimization settings.