numpy库_数组

深碍√TFBOYSˉ_ 2022-12-19 00:57 194阅读 0赞

### 目录 ###

*   *  slice()
     *  a\[m\]
     *  数组间的运算

import numpy as np
    a=np.random.random((7,4))
     
    print(a)
    print(a.ndim) # 数组维度
    print(a.shape) # 数组形状 几行几列
    print(a.size) # 数组元素总个数
    print(len(a)) # 行

[[ 0.55333763  0.44823165  0.15650461  0.81339595]
     [ 0.63970466  0.80740965  0.14827399  0.82013966]
     [ 0.96967462  0.29077142  0.32836976  0.98006694]
     [ 0.96021829  0.13743143  0.03275634  0.3651806 ]
     [ 0.94642223  0.77648366  0.97311496  0.56987987]
     [ 0.38355821  0.42780274  0.44693499  0.52726575]
     [ 0.99946457  0.90070665  0.11409929  0.31214208]]
    2
    (7, 4)
    28
    7

## slice() ##

s = slice(2) # 输出前两行
    print(a[s])

[[ 0.55333763  0.44823165  0.15650461  0.81339595]
     [ 0.63970466  0.80740965  0.14827399  0.82013966]]

s = slice(3) # 输出前三行
    print(a[s])

[[ 0.55333763  0.44823165  0.15650461  0.81339595]
     [ 0.63970466  0.80740965  0.14827399  0.82013966]
     [ 0.96967462  0.29077142  0.32836976  0.98006694]]

s = slice(2,7,2)   # 从索引 2 开始到索引 7 停止，间隔为2
    print(a[s]) # 输出第三行、第五行、第七行

[[ 0.96967462  0.29077142  0.32836976  0.98006694]
     [ 0.94642223  0.77648366  0.97311496  0.56987987]
     [ 0.99946457  0.90070665  0.11409929  0.31214208]]

s = slice(2,7) # 输出第三四五六七行
    print(a[s])

[[ 0.96967462  0.29077142  0.32836976  0.98006694]
     [ 0.96021829  0.13743143  0.03275634  0.3651806 ]
     [ 0.94642223  0.77648366  0.97311496  0.56987987]
     [ 0.38355821  0.42780274  0.44693499  0.52726575]
     [ 0.99946457  0.90070665  0.11409929  0.31214208]]

s = slice(2,5) # 输出三四五行
    print(a[s])

[[ 0.96967462  0.29077142  0.32836976  0.98006694]
     [ 0.96021829  0.13743143  0.03275634  0.3651806 ]
     [ 0.94642223  0.77648366  0.97311496  0.56987987]]

s = slice(-5，-2) 
    print(a[s])

File "<ipython-input-63-05aa4d8a3c24>", line 1
        s = slice(-5，-2)
                    ^
    SyntaxError: invalid character in identifier

## a\[m\] ##

print(a[2]) # 输出第三行

[ 0.96967462  0.29077142  0.32836976  0.98006694]

print(a[2:3]) # 输出第三行

[[ 0.96967462  0.29077142  0.32836976  0.98006694]]

print(a[2:5]) # 输出三四五行

[[ 0.96967462  0.29077142  0.32836976  0.98006694]
     [ 0.96021829  0.13743143  0.03275634  0.3651806 ]
     [ 0.94642223  0.77648366  0.97311496  0.56987987]]

print(a[-1]) # 输出最后一行

[ 0.99946457  0.90070665  0.11409929  0.31214208]

print(a[-4:-1]) # 输出倒数第四三二行

[[ 0.96021829  0.13743143  0.03275634  0.3651806 ]
     [ 0.94642223  0.77648366  0.97311496  0.56987987]
     [ 0.38355821  0.42780274  0.44693499  0.52726575]]

print(a[-5:-2:2]) # -5 -3 倒数第三倒数第五行

[[ 0.96967462  0.29077142  0.32836976  0.98006694]
     [ 0.94642223  0.77648366  0.97311496  0.56987987]]

print(a.flatten()) # 对该数组进行降维，返回一个一维数组

[ 0.55333763  0.44823165  0.15650461  0.81339595  0.63970466  0.80740965
      0.14827399  0.82013966  0.96967462  0.29077142  0.32836976  0.98006694
      0.96021829  0.13743143  0.03275634  0.3651806   0.94642223  0.77648366
      0.97311496  0.56987987  0.38355821  0.42780274  0.44693499  0.52726575
      0.99946457  0.90070665  0.11409929  0.31214208]

print(np.square(a)) # 对该数组中元素进行开方生成一个新的数组

[[ 0.30618254  0.20091161  0.02449369  0.66161297]
     [ 0.40922206  0.65191034  0.02198518  0.67262906]
     [ 0.94026886  0.08454802  0.1078267   0.9605312 ]
     [ 0.92201916  0.0188874   0.00107298  0.13335687]
     [ 0.89571503  0.60292688  0.94695273  0.32476306]
     [ 0.1471169   0.18301519  0.19975088  0.27800917]
     [ 0.99892943  0.81127248  0.01301865  0.09743268]]

## 数组间的运算 ##

import numpy as np
    b = np.random.random((3, 3))
    c = np.random.random((3, 3))
    print(b*c)
    print(b/c)
    print(b//c)

[[ 0.29335225  0.00147502  0.67270024]
     [ 0.62396253  0.03563709  0.05902942]
     [ 0.31935278  0.05229887  0.22414777]]
    [[ 2.34734326  0.27844557  0.89863309]
     [ 0.93940707  1.31942779  7.47228758]
     [ 0.83732892  2.34857493  1.79404377]]
    [[ 2.  0.  0.]
     [ 0.  1.  7.]
     [ 0.  2.  1.]]

import numpy as np
    b = [[1,2,3],[4,5,6],[7,8,9]],[[0,1,2],[3,4,5,],[6,7,8]],[[-1,0,1,],[2,3,4],[5,6,7]]
    c = [[0,2,3],[4,5,6],[7,8,9]],[[0,1,2],[3,4,5,],[6,7,8]],[[-1,0,1,],[2,3,4],[5,6,7]]
    print(b==c)

False