notebook.community

Edit and run



In [1]:

    
from platform import python_version



In [2]:

    
python_version()









    Out[2]:





'3.6.7'



In [3]:

    
import numpy as np



In [4]:

    
np.__version__









    Out[4]:





'1.16.3'

reverse



In [5]:

    
myarray = np.array([1,2,3])
myarray[::-1]









    Out[5]:





array([3, 2, 1])



In [6]:

    
myarray = np.array([
    [1,2,3],
    [4,5,6],
    [7,8,9]
])
myarray[::-1]









    Out[6]:





array([[7, 8, 9],
       [4, 5, 6],
       [1, 2, 3]])

scientific notation



In [7]:

    
# np.set_printoptions(edgeitems=3,infstr='inf',
# linewidth=75, nanstr='nan', precision=8,
# suppress=False, threshold=1000, formatter=None)

y=np.array([1.0e-10,1.0,100,1000])
y









    Out[7]:





array([1.e-10, 1.e+00, 1.e+02, 1.e+03])



In [8]:

    
np.set_printoptions(suppress=True)
y









    Out[8]:





array([   0.,    1.,  100., 1000.])

selecting



In [9]:

    
myarray = np.array([
    [1,2,3],
    [4,5,6],
    [7,8,9]
])
myarray









    Out[9]:





array([[1, 2, 3],
       [4, 5, 6],
       [7, 8, 9]])



In [10]:

    
myarray[:,1]









    Out[10]:





array([2, 5, 8])



In [11]:

    
myarray[0,:]









    Out[11]:





array([1, 2, 3])



In [12]:

    
x = np.array([
    [1,2,3],
    [4,5,6]
])



In [13]:

    
y = x.copy()



In [14]:

    
y.fill(1)



In [15]:

    
x









    Out[15]:





array([[1, 2, 3],
       [4, 5, 6]])



In [16]:

    
y









    Out[16]:





array([[1, 1, 1],
       [1, 1, 1]])

add row to multimensional array



In [17]:

    
myarray = np.array([
    [1,2,3],
    [4,5,6]
])



In [18]:

    
newrow = np.array([9,9,9])



In [19]:

    
np.vstack([myarray,newrow])









    Out[19]:





array([[1, 2, 3],
       [4, 5, 6],
       [9, 9, 9]])

add column



In [20]:

    
myarray = np.array([
    [1,2,3],
    [4,5,6]
])



In [21]:

    
newcol = np.array([[9],[9]])



In [22]:

    
np.hstack([myarray,newcol])









    Out[22]:





array([[1, 2, 3, 9],
       [4, 5, 6, 9]])

compare equality



In [28]:

    
a = np.array([1,2,3])
b = np.array([0,0,0])
np.array_equal(a,b)









    Out[28]:





False



In [32]:

    
a = np.array([1,np.nan,3])
b = np.array([1,np.nan,3])

np.array_equal(a,b)









    Out[32]:





False



In [33]:

    
a = np.array([1,np.nan,3])
b = np.array([1,np.nan,3])
np.allclose(a, b, equal_nan=True)









    Out[33]:





True



In [30]:

    
a = np.array([1,2,3])
b = np.array([1,2,3])

np.array_equal(a,b)









    Out[30]:





True