CODEWITHSUNDEEP
sympy
Felix
Felix

Reputation: 21

Why doesn't SymPy replace exponentials?

Simple example:

from sympy import *
n = symbols('n',integer=True)
x,y = symbols('x,y')
expression = exp(I*n*x)
expression.subs(exp(I*n),y)
#>> exp(I*n*x)

Why doesn't SymPy replace the exp(I*x) to give y**n? It works perfectly fine the other way around (replacing y in y**n with exp(I*x) to give exp(I*n*x)). Is there a hack to get this done?

Upvotes: 2

Views: 92

Answers (1)

asmeurer
asmeurer

Reputation: 91500

subs might not work in general if the expression you are replacing doesn't appear exactly in the expression.

One workaround is to use replace with pattern matching to replace a more general pattern

>>> a = Wild('a')
>>> expression.replace(exp(I*n*a), y**a)
y**x

Upvotes: 2

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