Append data to numpy string

Question

for some reason I can't append data to a numpy string.

for b in range(len(aUnique)):
    temp = aUnique[b]
    print(temp)
    numpy.append(sGewiss, temp)
    #RawData.cell(row=b+1, column=1).value = temp

print(sGewiss)

When I print "temp" I can see the right values so the loop is working correctly but when I print the array "sGewiss" I cannot see the new values added but only the old [66830 72312 72812].

Am I using the parameters wrong? Is there a dimension issue I am not aware of?

Thank you

I tried to add around 100 numbers to my array "sGweiss" which contains only 3 values. I was expecting an array containing the starting 3 elements plus the new 100 elements

the NumPy append method does not work "in-place" on the array that you pass it, i.e., it will not change sGewiss but will instead return a new array that is sGewiss appended with temp. You therefore have to store the return value, e.g., sGewiss = np.append(sGewiss, temp). — Matt Pitkin
– Matt Pitkin, Commented Dec 14, 2022 at 9:49
this kind of iterative appending is ok with list, but not with arrays. The 'numpy string' in the subject line does not make sense. — hpaulj
– hpaulj, Commented Dec 14, 2022 at 15:44

Mehdi Hamzezadeh · Accepted Answer · 2022-12-14 09:52:09Z

1

you should use :

    sGewiss = numpy.append(sGewiss, temp)

This is because NumPy append function creates a new NumPy array and returns the desired output. It does not change the input array in place.

edited Dec 14, 2022 at 9:52

answered Dec 14, 2022 at 9:39

Mehdi Hamzezadeh

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2 Comments

Dedder Over a year ago

Hi, thank you for your answer. sGewiss is a numpy list. If i use "sGewiss.append(temp)" i get an attribute error. AttributeError: 'numpy.ndarray' object has no attribute 'append'

Mehdi Hamzezadeh Over a year ago

I updated my answer. that should work.

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