Python在while和for循环中的索引问题

Question

我正在修改Schorsch在While loop inside for loop in Matlab中的答案，以便在Python3.5中针对我的问题使用。

我想迭代我的t数组中的值。对于每个值，如果我的计算结果是z收敛的(或者在最大值no之后不收敛)。)我将其复制到一个数组中。然后我画出结果。

import numpy as np
import matplotlib.pyplot as plt

maxiter = 100 # max no. iterations in convergence loop
t = 0.05*np.arange(10)
z = 0.1 # initial guess
x = np.zeros(len(t)) # array for results
cvec = np.zeros(len(t)) # does loop converge?

for ii in t:

    print(ii)

    convergence = 0

    while convergence == 0:

        z_old = z
        z = ii*np.random.rand() # perform calculations

        # check convergence

        if abs(z-z_old) < 0.01: # convergence
            # store result
            convergence = 1
            x[ii] = z
            cvec[ii] = convergence

        elif abs(z-z_old) >= 0.01 and ii < maxiter: # no convergence but loop again
            convergence = 0
        else: # no convergence, move on to next value in t array
            convergence = 0
            x[ii] = 1e3
            cvec[ii] = convergence
            break

# plot result
plt.figure()
plt.plot(t[cvec==1],x[cvec==1],'x')
plt.xlabel('t')
plt.ylabel('x')
plt.show()

我收到一个错误：VisibleDeprecationWarning: using a non-integer number instead of an integer will result in an error in the future lines = """

这是否意味着我必须改变我对while或for循环的索引方式，如果是的话，我应该如何做呢？

Answer 1

这个问题与行x[ii] =和cvec[ii]有关。当您试图访问非整数索引时。这些索引是在以下行生成的：

(...)
t = 0.05*np.arange(10) #[ 0.  ,  0.05,  0.1 ,  0.15,  0.2 ,  0.25,  0.3 ,  0.35,  0.4 ,  0.45]
(...)

要解决这个问题，有几种方法可以这样做，但最简单的方法是访问t变量的值所在的相同索引。

import numpy as np
import matplotlib.pyplot as plt

maxiter = 100 # max no. iterations in convergence loop
t = 0.05*np.arange(10)
z = 0.1 # initial guess
x = np.zeros(len(t)) # array for results
cvec = np.zeros(len(t)) # does loop converge?

for idx, ii in enumerate(t):

    print(ii)

    convergence = 0

    while convergence == 0:

        z_old = z
        z = ii*np.random.rand() # perform calculations

        # check convergence

        if abs(z-z_old) < 0.01: # convergence
            # store result
            convergence = 1
            x[idx] = z
            cvec[idx] = convergence

        elif abs(z-z_old) >= 0.01 and ii < maxiter: # no convergence but loop again
            convergence = 0
        else: # no convergence, move on to next value in t array
            convergence = 0
            x[idx] = 1e3
            cvec[idx] = convergence
            break

# plot result
plt.figure()
plt.plot(t[cvec==1],x[cvec==1],'x')
plt.xlabel('t')
plt.ylabel('x')
plt.show()

使用while循环迭代值的最大次数，而不收敛

import numpy as np
import matplotlib.pyplot as plt

maxiter = 100 # max no. iterations in convergence loop
t = 0.05*np.arange(10)
z = 0.1 # initial guess
x = np.zeros(len(t)) # array for results
cvec = np.zeros(len(t)) # does loop converge?

for idx, ii in enumerate(t):

    print(ii)

    # Assume it wont converge
    # So if we loop through all the max iterations and still no convergence, it is already marked
    x[idx] = 1e3
    cvec[idx] = 0

    while iter in range(maxiter):

        z_old = z
        z = ii*np.random.rand() # perform calculations

        if abs(z-z_old) < 0.01: # converge, therefore stop looping
            x[idx] = z
            cvec[idx] = 1
            break

# plot result
plt.figure()
plt.plot(t[cvec==1],x[cvec==1],'x')
plt.xlabel('t')
plt.ylabel('x')
plt.show()