python - 类型错误 : unsupported operand type(s) for ** or pow(): 'list' and 'int' . plt.plot

Question

当我编写以下代码时，出现以下错误。我做错了什么？？

def f(t):
    return np.sin(t**2)

n = 20  # number of points for Riemann integration
a = 0; b = 2
P = np.linspace(a, b, n)  # Standard partition constant width
dt = (b-a)/n
T = [np.random.rand()*dt + p for p in P[:-1]]  # Randomly chosen point

再做一些事情，然后:

plt.figure(figsize=(10,10))

plt.plot(T, f(T), '.', markersize=10)
plt.bar(P[:-1], f(T), width=dt, alpha=0.2, align='edge')

x = np.linspace(a, b, n*100)  # we take finer spacing to get a "smooth" graph
y = f(x)
plt.plot(x, y)
plt.title('Riemann sum with n = {} points'.format(n))
plt.axis('off')
plt.show()

最后我得到以下错误:

    Traceback (most recent call last):
    File "riman.py", line 35, in <module>
    plt.plot(T, f(T), '.', markersize=10)
    File "riman.py", line 11, in f
    return np.sin(t**2)
TypeError: unsupported operand type(s) for ** or pow(): 'list' and 'int'

Answer 1

错误消息是不言自明的 - 没有为内置 list 类型定义幂运算符 **。

它们是但是为np.array定义的:

>>> np.array(range(5))**2
array([ 0,  1,  4,  9, 16])

修复:

T = np.array([np.random.rand()*dt + p for p in P[:-1]])