如何将字符串数组转换为numpy中的浮点数组？

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问题：如何将字符串数组转换为numpy中的浮点数组？

如何转换

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

至

[1.1, 2.2, 3.2]

在NumPy中？

How to convert

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

[1.1, 2.2, 3.2]

in NumPy?

回答 0

好吧，如果您是以列表的形式读取数据，则可以这样做np.array(map(float, list_of_strings))（或等效地，使用列表理解）。（在Python 3，你需要调用list的map，如果你使用的返回值map，因为map现在返回一个迭代器）。

但是，如果已经是一串Numpy的字符串，则有更好的方法。使用astype()。

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

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)

回答 1

您也可以使用它

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

回答 2

另一个选项可能是numpy.asarray：

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

对于Python 2 *：

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

导致：

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

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

resulting in:

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

回答 3

如果您拥有（或创建）单个字符串，则可以使用np.fromstring：

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

注意，x = ','.join(x)将x数组转换为string '1.1, 2.2, 3.2'。如果您从txt文件中读取一行，则每一行都已经是一个字符串。

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.

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