本文已参与「新人创作礼」活动，一起开启掘金创作之路。
Trick：纯demo，心在哪里，结果就在那里（ipython notebook代码演示）
5
import numpy as np
a = np.array([[1,2,3,4],[2,3,4,5]])
print (a)
[[1 2 3 4]
[2 3 4 5]]
9
import numpy as np
a = np.array([1,2,3,4],ndmin = 3)
print (a)
[[[1 2 3 4]]]
11
import numpy as np
dt = np.dtype(np.int32)
print dt
File "<ipython-input-11-96707a7b8c9c>", line 3
print dt
^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(dt)?
13
import numpy as np
x = np.array([1,2,3,4,5,6])
print (x.flags)
C_CONTIGUOUS : True
F_CONTIGUOUS : True
OWNDATA : True
WRITEABLE : True
ALIGNED : True
WRITEBACKIFCOPY : False
UPDATEIFCOPY : False
16
import numpy as np
x = np.empty([3,2], dtype = int)
print(x)
[[1 2]
[3 4]
[5 6]]
41
import numpy as np
s = 'Hello World'
a = np.frombuffer(s, dtype = 'S1')
print (a)
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-41-30ab03270588> in <module>
1 import numpy as np
2 s = 'Hello World'
----> 3 a = np.frombuffer(s, dtype = 'S1')
4 print (a)
AttributeError: 'str' object has no attribute '__buffer__'
42
# 从列表中获得迭代器
import numpy as np
list = range(5)
it = iter(list)
# 使用迭代器创建 ndarray
x = np.fromiter(it, dtype = float)
print (x)
[0. 1. 2. 3. 4.]
3
import numpy as np
x = np.linspace(10,20,5)
print(x)
[10. 12.5 15. 17.5 20. ]
3
import numpy as np
#显示该数组中（0，0），（1，1），（2，0）位置的元素
x = np.array([[1, 2], [3, 4], [5, 6]])
y = x[[0,1,2],[0,1,0]]
print(y)
[1 4 5]
7
import numpy as np
a = np.arange(8).reshape(2,4)
print ('原数组：')
print (a)
print ('\n')
print ('调用 ravel 函数之后：')
print (a.ravel())
print ('\n')
print ('以 F 风格顺序调用 ravel 函数之后：')
print (a.ravel(order = 'F') )
原数组：
[[0 1 2 3]
[4 5 6 7]]
调用 ravel 函数之后：
[0 1 2 3 4 5 6 7]
以 F 风格顺序调用 ravel 函数之后：
[0 4 1 5 2 6 3 7]
17
import time
s= time.time()
time.sleep(2)
print(s)
p = time.time()
print(p)
q = p s
print(q)
1568959868.6637378
1568959870.6643877
2.000649929046631
26
import time
s = 1568959868.6637378
t = time.localtime(s)
w = time.strftime("%Y-%m-%d %H:%M:%S",t)
print(w)
2019-09-20 14:11:08
