Python:分段函数积分错误: "TypeError: cannot determine truth value of ..."

Question

这段代码运行正确:

import sympy as sp

def xon (ton, t):
    return (t-ton)/5

xonInt = sp.integrate (xon(ton, t),t)

print xonInt

但是当函数变得分段时，例如:

import sympy as sp

def xon (ton, t):
    if ton <= t:
        return (t-ton)/5
    else:
        return 0

xonInt = sp.integrate (xon(ton, t),t)

print xonInt

我收到以下错误:

File "//anaconda/lib/python2.7/site-packages/sympy/core/relational.py", line > 103, in nonzero raise TypeError("cannot determine truth value of\n%s" % self)

TypeError: cannot determine truth value of ton <= t

据我了解，该错误是由于 ton 和 t 都可以是正数和负数。这是对的吗？如果我为 t 设置正积分限制，错误不会消失。如何计算给定分段函数的积分？

更新:该功能的更新版本，有效:

import sympy as sp

t = sp.symbols('t')   
ton = sp.symbols('ton')
xon = sp.Piecewise((((t-ton)/5), t <= ton), (0, True))

xonInt = sp.integrate (xon,t)
print xonInt

Answer 1

分段类

您需要使用sympy Piecewise class .

正如评论中所建议的:

Piecewise(((t - ton)/5, ton <= t), (0, True))