How to convert an array of strings to an array of floats in numpy?

Another option might be numpy.asarray:

import numpy as np
a = ["1.1", "2.2", "3.2"]
b = np.asarray(a, dtype=float)

print(a, type(a), type(a[0]))
print(b, type(b), type(b[0]))

resulting in:

['1.1', '2.2', '3.2'] <class 'list'> <class 'str'>
[1.1 2.2 3.2] <class 'numpy.ndarray'> <class 'numpy.float64'>

Well, if you're reading the data in as a list, just do np.array(map(float, list_of_strings)) (or equivalently, use a list comprehension). (In Python 3, you'll need to call list on the map return value if you use map, since map returns an iterator now.)

However, if it's already a numpy array of strings, there's a better way. Use astype().

import numpy as np
x = np.array(['1.1', '2.2', '3.3'])
y = x.astype(np.float)