Using python type hints with numba

Question

From the numba website:

from numba import jit

@jit
def f(x, y):
    # A somewhat trivial example
    return x + y

Is there a way to have numba use python type hints (if provided)?

Answer 1

Yes and no. You can simply use the normal python syntax for annotations (the jit decorator will preserve them). Building on your simple example:

from numba import jit

@jit
def f(x: int, y: int) -> int:
    # A somewhat trivial example
    return x + y

>>> f.__annotations__
{'return': int, 'x': int, 'y': int}
>>> f.signatures  # they are not recognized as signatures for jit
[]

However to explicitly (enforce) the signature it must be given in the jit-decorator:

from numba import int_

@jit(int_(int_, int_))
def f(x: int, y: int) -> int:
    # A somewhat trivial example
    return x + y

>>> f.signatures
[(int32, int32)]  # may be different on other machines

There is as far as I know no automatic way for jit to understand the annotations and build its signature from these.