# NumPy - 数组创建例程

## `numpy.empty`

``````numpy.empty(shape, dtype = float, order = 'C')
``````

1. `Shape` 空数组的形状，整数或整数元组
2. `Dtype` 所需的输出数组类型，可选
3. `Order` `'C'`为按行的 C 风格数组，`'F'`为按列的 Fortran 风格数组

### 示例

``````import numpy as np
x = np.empty([3,2], dtype =  int)
print x
``````

``````[[22649312    1701344351]
[1818321759  1885959276]
[16779776    156368896]]
``````

## `numpy.zeros`

``````numpy.zeros(shape, dtype = float, order = 'C')
``````

1. `Shape` 空数组的形状，整数或整数元组
2. `Dtype` 所需的输出数组类型，可选
3. `Order` `'C'`为按行的 C 风格数组，`'F'`为按列的 Fortran 风格数组

### 示例 1

``````# 含有 5 个 0 的数组，默认类型为 float
import numpy as np
x = np.zeros(5)
print x
``````

``````[ 0.  0.  0.  0.  0.]
``````

### 示例 2

``````import numpy as np
x = np.zeros((5,), dtype = np.int)
print x
``````

``````[0  0  0  0  0]
``````

### 示例 3

``````# 自定义类型
import numpy as np
x = np.zeros((2,2), dtype =  [('x',  'i4'),  ('y',  'i4')])
print x
``````

``````[[(0,0)(0,0)]
[(0,0)(0,0)]]
``````

## `numpy.ones`

``````numpy.ones(shape, dtype = None, order = 'C')
``````

1. `Shape` 空数组的形状，整数或整数元组
2. `Dtype` 所需的输出数组类型，可选
3. `Order` `'C'`为按行的 C 风格数组，`'F'`为按列的 Fortran 风格数组

### 示例 1

``````# 含有 5 个 1 的数组，默认类型为 float
import numpy as np
x = np.ones(5)  print x
``````

``````[ 1.  1.  1.  1.  1.]
``````

### 示例 2

``````import numpy as np
x = np.ones([2,2], dtype =  int)
print x
``````

``````[[1  1]
[1  1]]
``````