One of the string arrays is not sorted

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import numpy as np

arr1=np.array(['102.0','135.0','135.0','152.0','93.0','95.0'])

print(arr1)
arr1.sort()
print(arr1)

print()

arr2=np.array(['86.0','82.0','84.0','87.0','95.0','89.0'])

print(arr2)
arr2.sort()
print(arr2)

The first array is not sorted, but second is sorted, why?. I cannot find the mistake.

python-3.x sorting python
2 Answers

The sort function only sorts integers correctly, so for strings it sorts by the first character so the ones over a hundred will be before the one that are ninety something, the way to fix would be to change them to integers:

import numpy as np

arr1=np.array(['102.0','135.0','135.0','152.0','93.0','95.0'])
arr1 = arr1.astype(float)
print(arr1)
arr1.sort()
print(arr1)

print()

arr2=np.array(['86.0','82.0','84.0','87.0','95.0','89.0'])
arr2 = arr2.astype(float)
print(arr2)
arr2.sort()
print(arr2)

As @juanpa.arrivillaga mentioned:

it sorts lexicographically by all the characters

user_87083640

You are sorting strings the sort function is properly sorting the string elements (e.g. "102.0" comes before "93.0"). If you want to sort integers properly, remove the double-quotes around all your elements:

arr1=np.array([102.0,135.0,135.0,152.0,93.0,95.0])
arr2=np.array([86.0,82.0,84.0,87.0,95.0,89.0])
user_95620030
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