# 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?

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)
``````

You can use this as well

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

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.

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

resulting in:

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

You can use `np.array()` with `dtype = float`:

``````import numpy as np

x = ["1.1", "2.2", "3.2"]
y = np.array(x,dtype=float)
``````

Output:

``````array([1.1, 2.2, 3.2])
``````
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