Python How to convert ['0.12' '0.23'] <class 'numpy.ndarray'> to a normal numpy array

Question

I am using a package that is fetching values from a csv file for me. If I print out the result I get ['0.12' '0.23'] . I checked the type, which is <class 'numpy.ndarray'> I want to convert it to a numpy array like [0.12, 0.23] . I tried np.asarray(variabel) but that did not resolve the problem.

Answer 1

Solution

import numpy as np
array = array.astype(np.float)


# If you are just initializing array you can do this
ar= np.array(your_list,dtype=np.float)

Answer 2

It might help to know how the csv was read. But for what ever reason it appears to have created a numpy array with a string dtype :

In [106]: data = np.array(['0.12', '0.23'])
In [107]: data
Out[107]: array(['0.12', '0.23'], dtype='<U4')
In [108]: print(data)
['0.12' '0.23']

The str formatting of such an array omits the comma, the repr display keeps it.

A list equivalent also displays with comma:

In [109]: data.tolist()
Out[109]: ['0.12', '0.23']

We call this a numpy array, but technically it is of class numpy.ndarray

In [110]: type(data)
Out[110]: numpy.ndarray

It can be converted to an array of floats with:

In [111]: data.astype(float)
Out[111]: array([0.12, 0.23])

It is still a ndarray , just the dtype is different. You may need to read more in the numpy docs about dtype .

The error:

If I want to calculate with it it gives me an error TypeError: only size-1 arrays can be converted to Python scalars

has a different source. data has 2 elements. You don't show the code that generates this error, but often we see this in plotting calls. The parameter is supposed to be a single number (often an integer), where as your array, even with a numeric dtype ) is two numbers.