Sympy:指数乘而不是总和的指数 [英] Sympy: Multiplications of exponential rather than exponential of sum

问题描述

我正在搜索如何告诉SymPy使用指数的乘法而不是总和的指数.也就是说，当前它给我exp(a + b)，而我想得到exp(a)* exp(b).一定有一种相当简单的方法，但是我似乎找不到它.

I'm searching how to tell SymPy to use a multiplication of exponentials rather than an exponential of a sum. That is, it currently gives me exp(a + b) and I would want to get exp(a)*exp(b). There must be a fairly easy way but I can't seem to find it.

推荐答案

您可以使用

You could use the expand() function to show the expression with multiplication of bases rather than the sum of exponents:

>>> from sympy import *
>>> a, b = symbols('a b')
>>> expr = exp(a + b)
>>> expr
exp(a + b)
>>> expr.expand()
exp(a)*exp(b)

此功能的文档位于此处.相关部分总结如下:

The documentation for this function is here. The relevant parts are summarised below:

sympy.core.function.expand(e, deep=True, modulus=None, power_base=True, power_exp=True, mul=True, log=True, multinomial=True, basic=True, **hints)

使用作为提示给出的方法来扩展表达式.

Expand an expression using methods given as hints.

除非明确设置为False，否则评估的提示为:basic，log， multinomial，mul，power_base和power_exp ...

Hints evaluated unless explicitly set to False are: basic, log, multinomial, mul, power_base, and power_exp ...

很明显，power_exp是相关提示:

power_exp

将指数中的加法扩展为乘法的底数.

Expand addition in exponents into multiplied bases.

>>> exp(x + y).expand(power_exp=True)
exp(x)*exp(y)
>>> (2**(x + y)).expand(power_exp=True)
2**x*2**y

将其转到False可使表达式保持不变:

Turning it to False leaves the expression unchanged:

>>> expr.expand(power_exp=False)
exp(a + b)

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