Home/ Questions/How to fix "the truth value of an array with more than one element is ambiguous. use a.any() or a.all()"?
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dubuquereta
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Asked: 2022-05-05T03:35:46+00:00 In:

How to fix “the truth value of an array with more than one element is ambiguous. use a.any() or a.all()”?

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I’m building a new program, but when I run it, an error pops up. The error displayed is as follows: 

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

I have tried several workarounds, but they still do not get the desired results. If you have come across this situation and have a solution for the truth value of an array with more than one element is ambiguous. use a.any() or a.all() problem, pls let me know.  This is what I do: 

r = mlab.csv2rec(datafile, delimiter=',', names=COL_HEADERS)
mask = ((r["dt"] >= startdate) and (r["dt"] <= enddate))
selected = r[mask]

Thanks.

numnumpy
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3 Answers

  1. Best Answer

    This error message suggests that you should use a.any() or a.all() instead of the and  operator. However I usually solve this problem using the numpy.logical_and(a,b) method.

    Here is the code after editing

    
 mask = numpy.logical_and(r["dt"] >= startdate, r["dt"] <= enddate)
 selected  = r[mask]
    • 20

  2. Another method I think it is useful:

    • if np.array([]).size: print(1) fixxed the error.
    • You also consider the more pythonic as below:

      if np.array([]) is not None: print(1)

    • 15

  3. Simply using a numpy.logical_and(a,b) would work. You could modify the code to be:

    selected = r[numpy.logical_and(r["dt"] >= startdate, r["dt"] <= enddate)]
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