CODEWITHSUNDEEP
pythonstringnumpyfloating-point
user2558887
user2558887

Reputation:

Numpy Convert String to Float when Possible

Suppose I have a list

mix = numpy.array(['1.', '2.', 'a'])

How can I convert string to float when possible, so that I could get:

array([1., 2., 'a'])

I try to use try / exception with astype(), but it won't convert a single element.

Update: In csv package, there is csv.QUOTE_NONNUMERIC, I am wondering if numpy supports something similar.

Upvotes: 3

Views: 5520

Answers (3)

Davide Fiocco
Davide Fiocco

Reputation: 5914

One way that might work is checking if the string matches a number with a regex, and if so convert to float:

[float(x) if re.search('[0-9]*\.?[0-9]', x) else x for x in mix]

Upvotes: 0

mrcl
mrcl

Reputation: 2190

Didn't find a function to make it work, so I wrote something that works for you.

def myArrayConverter(arr):

    convertArr = []
    for s in arr.ravel():    
        try:
            value = float32(s)
        except ValueError:
            value = s

        convertArr.append(value)

    return array(convertArr,dtype=object).reshape(arr.shape)

Cheers

Upvotes: 5

Irshad Bhat
Irshad Bhat

Reputation: 8709

For arrays of mixed datatypes set dtype=object: 

>>> mix = numpy.array(['1.', '2.', 'a'])
>>> mixed=[]
>>> for a in list(mix):
       try:
         mixed.append(float(a))
       except:
         mixed.append(a)

>>> mixed=numpy.array(mixed, dtype=object)
>>> mixed
array([1.0, 2.0, 'a'], dtype=object)
>>> type(mixed[0]),type(mixed[1]),type(mixed[2])
(<type 'float'>, <type 'float'>, <type 'numpy.string_'>)

Hope it hepls.

Upvotes: 2

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