numpy ndarray object has no attribute append

Question

This is part of my code, why it shows error. thanks in advance

prets = []
pvols = []
for p in range (2500):
    weights = np.random.random(noa)
    weights /= np.sum(weights)
    prets.append(np.sum(rets.mean() * weights) * 252)
    pvols.append(np.sqrt(np.dot(weights.T,
                                np.dot(rets.cov() * 252, weights))))
    prets = np.array(prets)
    pvols = np.array(pvols)

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-220-3a3ff7a7f33e> in <module>
      4     weights = np.random.random(noa)
      5     weights /= np.sum(weights)
----> 6     prets.append(np.sum(rets.mean() * weights) * 252)
      7     pvols.append(np.sqrt(np.dot(weights.T,
      8                                 np.dot(rets.cov() * 252, weights))))

AttributeError: 'numpy.ndarray' object has no attribute 'append'

Comments

Can you share your complete code? It is difficult to understand the flow of your code.

Answer 1

Hi@Noman,

You created two empty list. And in the for loop you tried to append values in your list. But in the last part you tried to convert your list into numpy array using the same variable name. So I suggest you to change your variable name as given below.

prets = []
pvols = []
for p in range (2500):
    weights = np.random.random(noa)
    weights /= np.sum(weights)
    prets.append(np.sum(rets.mean() * weights) * 252)
    pvols.append(np.sqrt(np.dot(weights.T,
                                np.dot(rets.cov() * 252, weights))))
    pret = np.array(prets)
    pvol = np.array(pvols)

Make this changes in your code and try once again.

Comments

u didnt gave

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Can you explain your query?

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thank you !!!