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

### Question

How to convert

``````["1.1", "2.2", "3.2"]
``````

to

``````[1.1, 2.2, 3.2]
``````

in NumPy?

2018/06/12
1
119
6/12/2018 10:19:49 AM

### Accepted Answer

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)
``````
2017/06/30
181
6/30/2017 4:59:04 PM

You can use this as well

``````import numpy as np
x=np.array(['1.1', '2.2', '3.3'])
x=np.asfarray(x,float)
``````
2017/09/17

Another option might be numpy.asarray:

``````import numpy as np
a = ["1.1", "2.2", "3.2"]
b = np.asarray(a, dtype=np.float64, order='C')
``````

For Python 2*:

``````print a, type(a), type(a)
print b, type(b), type(b)
``````

resulting in:

``````['1.1', '2.2', '3.2'] <type 'list'> <type 'str'>
[1.1 2.2 3.2] <type 'numpy.ndarray'> <type 'numpy.float64'>
``````
2018/06/12

If you have (or create) a single string, you can use np.fromstring:

``````import numpy as np
x = ["1.1", "2.2", "3.2"]
x = ','.join(x)
x = np.fromstring( x, dtype=np.float, sep=',' )
``````

Note, `x = ','.join(x)` transforms the x array to string `'1.1, 2.2, 3.2'`. If you read a line from a txt file, each line will be already a string.

2017/10/05

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