整数值问题以及如何提供语法来描述 Python 中的 Int 值

Question

我目前遇到的错误描述为：仅整数、切片 (:)、省略号 (...)、numpy.newaxis (None) 和整数或布尔数组是有效的索引。我其实明白这个问题。但是我无法在 python 代码中修复它，因为我只是使用 Python 的初学者。完整代码在 link: 'https://homepages.ecs.vuw.ac.nz/~marslast/Code/Ch9/TSP.py' 终端报告是：

((1, 2, 3, 4, 0), 2.4225597326923185)
0.0004763603210449219
Greedy search
Traceback (most recent call last):
  File "TSP.py", line 183, in <module>
    runAll()
  File "TSP.py", line 167, in runAll
    print (greedy(distances))
  File "TSP.py", line 57, in greedy
    dist[:,cityOrder[0]] = np.Inf
IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices

无效代码：

    nCities = np.shape(distances)[0]
    distanceTravelled = 0
    
    # Need a version of the matrix we can trash
    dist = distances.copy()

    cityOrder = np.zeros(nCities)
    cityOrder[0] = np.random.randint(nCities)
    dist[:,cityOrder[0]] = np.Inf

    for i in range(nCities-1):
        cityOrder[i+1] = np.argmin(dist[cityOrder[i],:])
        distanceTravelled  += dist[cityOrder[i],cityOrder[i+1]]
        # Now exclude the chance of travelling to that city again
        dist[:,cityOrder[i+1]] = np.Inf
    
    # Now return to the original city
    distanceTravelled += distances[cityOrder[nCities-1],0]

    return cityOrder, distanceTravelled ```

Answer 1

问题来自 numpy.zeros（文档 here）的使用。可以看到，输出数组默认的dtype是float。而且你不能使用浮点数来索引数组。

快速解决方法是将 cityOrder 的 dtype 指定为 int:

 cityOrder = np.zeros(nCities, dtype=int)

整数值问题以及如何提供语法来描述 Python 中的 Int 值

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