I want to build a container of Hermite polynomials (link to scipy's hermite doc) of different orders. From what the doc says, I expect scipy.special.hermite to accept the order n and return a function - an Hermite polynomial of order n.
This seems to work fine with single functions. But when I try to use a list of Hermitte polynomials by realising them as lambda functions, it seems they will all be reset to the last polynomial:
from scipy.special import hermite
base_funcs = [lambda x: hermite(i)(x) for i in range(5)]
[f(1) for f in base_funcs]
Out[40]: [-20.0, -20.0, -20.0, -20.0, -20.0]
hermite(0)(1)
Out[41]: 1.0
hermite(4)(1)
Out[42]: -20.0
Is there a way to initiate a container of different Hermite polynomials properly, without previous elements being overwritten by subsequent ones in the container apprehension statement? Thanks!
As Warren's comment says, this is due to Python's late binding mechanism. To circumvent it, one solution is to include the loop variable as one of the function's default arguments. i.e.
[lambda x, i=i: hermite(i)(x) for i in range(5)]
Suggested reading: https://docs.python-guide.org/writing/gotchas/#late-binding-closures.