{"id":247,"date":"2022-08-23T21:53:54","date_gmt":"2022-08-23T13:53:54","guid":{"rendered":"http:\/\/162.14.82.114\/?p=247"},"modified":"2022-08-23T21:54:00","modified_gmt":"2022-08-23T13:54:00","slug":"numpy%e5%ad%a6%e4%b9%a0%e8%ae%b0%e5%bd%95%ef%bc%88%e4%b8%89%ef%bc%89","status":"publish","type":"post","link":"http:\/\/162.14.82.114\/index.php\/247\/08\/23\/2022\/","title":{"rendered":"Numpy\u5b66\u4e60\u8bb0\u5f55\uff08\u4e8c\uff09"},"content":{"rendered":"

Numpy\u9ad8\u7ea7\u7d22\u5f15<\/h2>\n

\u6574\u6570\u6570\u7ec4\u7d22\u5f15<\/h3>\n
import numpy as np \nx = np.array([[1,  2],  [3,  4],  [5,  6]]) \ny = x[[0,1,2],  [0,1,0]]  \ny\n# array([1, 4, 5])<\/code><\/pre>\n
import numpy as np\na = np.array([[1,2,3], [4,5,6],[7,8,9]])\nb = a[1:3, 1:3]\nc = a[1:3,[1,2]]\nd = a[...,1:]\nprint(b)\nprint(c)\nprint(d)\n#[[5 6]\n# [8 9]]\n#[[5 6]\n# [8 9]]\n#[[2 3]\n# [5 6]\n# [8 9]]<\/code><\/pre>\n
\u5e03\u5c14\u7d22\u5f15<\/h3>\n
import numpy as np \nx = np.array([[  0,  1,  2],[  3,  4,  5],[  6,  7,  8],[  9,  10,  11]])  \nprint  ('\u5927\u4e8e 5 \u7684\u5143\u7d20\u662f\uff1a')\nx[x >  5]\n# \u5927\u4e8e 5 \u7684\u5143\u7d20\u662f\uff1a\n# array([ 6,  7,  8,  9, 10, 11])<\/code><\/pre>\n
# \u4f7f\u7528 ~\uff08\u53d6\u8865\u8fd0\u7b97\u7b26\uff09\u6765\u8fc7\u6ee4 NaN\nimport numpy as np \na = np.array([np.nan,  1,2,np.nan,3,4,5])  \na[~np.isnan(a)]\n# array([1., 2., 3., 4., 5.])<\/code><\/pre>\n
# \u8fc7\u6ee4\u6389\u975e\u590d\u6570\u5143\u7d20\na = np.array([1,  2+6j,  5,  3.5+5j])  \na[np.iscomplex(a)]\n# array([2. +6.j, 3.5+5.j])<\/code><\/pre>\n
a = np.array([1,  2+6j,  5,  3.5+5j])  \na[~np.iscomplex(a)]\n# array([1.+0.j, 5.+0.j])<\/code><\/pre>\n
\u82b1\u5f0f\u7d22\u5f15<\/h3>\n
# \u4f20\u5165\u987a\u5e8f\u7d22\u5f15\u6570\u7ec4\nimport numpy as np \nx=np.arange(32).reshape((8,4))\nx[[4,2,1,7]]\n# array([[16, 17, 18, 19],\n#       [ 8,  9, 10, 11],\n#       [ 4,  5,  6,  7],\n#       [28, 29, 30, 31]])<\/code><\/pre>\n
# \u4f20\u5165\u5012\u5e8f\u7d22\u5f15\u6570\u7ec4\nx=np.arange(32).reshape((8,4))\nx[[-4,-2,-1,-7]]\n#array([[16, 17, 18, 19],\n#       [24, 25, 26, 27],\n#       [28, 29, 30, 31],\n#       [ 4,  5,  6,  7]])<\/code><\/pre>\n
# \u4f20\u5165\u591a\u4e2a\u7d22\u5f15\u6570\u7ec4\uff08\u8981\u4f7f\u7528np.ix_\uff09\nx=np.arange(32).reshape((8,4))\nx[np.ix_([1,5,7,2],[0,3,1,2])]\n# array([[ 4,  7,  5,  6],\n#       [20, 23, 21, 22],\n#       [28, 31, 29, 30],\n#       [ 8, 11,  9, 10]])<\/code><\/pre>\n
NumPy \u5e7f\u64ad(Broadcast)<\/h2>\n
# \u5982\u679c\u4e24\u4e2a\u6570\u7ec4 a \u548c b \u5f62\u72b6\u76f8\u540c\uff0c\u5373\u6ee1\u8db3 a.shape == b.shape\uff0c\u90a3\u4e48 a*b \u7684\u7ed3\u679c\u5c31\u662f a \u4e0e b \u6570\u7ec4\u5bf9\u5e94\u4f4d\u76f8\u4e58\u3002\na = np.array([1,2,3,4]) \nb = np.array([10,20,30,40]) \nc = a * b \nc\n# array([ 10,  40,  90, 160])<\/code><\/pre>\n
# \u5f53\u8fd0\u7b97\u4e2d\u7684 2 \u4e2a\u6570\u7ec4\u7684\u5f62\u72b6\u4e0d\u540c\u65f6\uff0cnumpy \u5c06\u81ea\u52a8\u89e6\u53d1\u5e7f\u64ad\u673a\u5236\u3002\na = np.array([[ 0, 0, 0],\n           [10,10,10],\n           [20,20,20],\n           [30,30,30]])\nb = np.array([0,1,2])\na + b\n# array([[ 0,  1,  2],\n#        [10, 11, 12],\n#        [20, 21, 22],\n#        [30, 31, 32]])<\/code><\/pre>\n
\n    
\"img\"<\/div>\n<\/div>\n
a = np.array([[ 0, 0, 0],\n           [10,10,10],\n           [20,20,20],\n           [30,30,30]])\nb = np.array([1,2,3])\nbb = np.tile(b, (4, 1))  # \u91cd\u590d b \u7684\u5404\u4e2a\u7ef4\u5ea6\na + bb\n# array([[ 1,  2,  3],\n#        [11, 12, 13],\n#        [21, 22, 23],\n#        [31, 32, 33]])<\/code><\/pre>\n
NumPy \u8fed\u4ee3\u6570\u7ec4<\/h2>\n
NumPy \u8fed\u4ee3\u5668\u5bf9\u8c61 numpy.nditer \u63d0\u4f9b\u4e86\u4e00\u79cd\u7075\u6d3b\u8bbf\u95ee\u4e00\u4e2a\u6216\u8005\u591a\u4e2a\u6570\u7ec4\u5143\u7d20\u7684\u65b9\u5f0f<\/p>\n
import numpy as np\n a = np.arange(6).reshape(2,3)\nfor x in np.nditer(a):\n    print (x, end=", " )\nprint ('\\n')\n# 0, 1, 2, 3, 4, 5, <\/code><\/pre>\n
a = np.arange(6).reshape(2,3)\n# \u9009\u62e9\u7684\u987a\u5e8f\u662f\u548c\u6570\u7ec4\u5185\u5b58\u5e03\u5c40\u4e00\u81f4\u7684\uff0c\u8fd9\u6837\u505a\u662f\u4e3a\u4e86\u63d0\u5347\u8bbf\u95ee\u7684\u6548\u7387\uff0c\u9ed8\u8ba4\u662f\u884c\u5e8f\u4f18\u5148\nfor x in np.nditer(a.T):\n    print (x, end=", " )\nprint ('\\n')\n\n# a.T.copy(order = 'C') \u7684\u904d\u5386\u7ed3\u679c\u9ed8\u8ba4\u662f\u6309\u884c\u8bbf\u95ee\nfor x in np.nditer(a.T.copy(order='C')):\n    print (x, end=", " )\nprint ('\\n')\n# 0, 1, 2, 3, 4, 5, \n# 0, 3, 1, 4, 2, 5, <\/code><\/pre>\n
\u63a7\u5236\u904d\u5386\u987a\u5e8f<\/h3>\n
for x in np.nditer(a, order='F')      #:Fortran order\uff0c\u5373\u662f\u5217\u5e8f\u4f18\u5148\uff1b\nfor x in np.nditer(a.T, order='C')    #:C order\uff0c\u5373\u662f\u884c\u5e8f\u4f18\u5148\uff1b<\/code><\/pre>\n
import numpy as np \n\na = np.arange(0,60,5) \na = a.reshape(3,4)  \nprint ('\u539f\u59cb\u6570\u7ec4\u662f\uff1a')\nprint (a)\nprint ('\u4ee5 C \u98ce\u683c\u987a\u5e8f\u6392\u5e8f\uff1a')\nfor x in np.nditer(a, order =  'C'):  \n    print (x, end=", " )\nprint ('\u4ee5 F \u98ce\u683c\u987a\u5e8f\u6392\u5e8f\uff1a')\nfor x in np.nditer(a, order =  'F'):  \n    print (x, end=", " )<\/code><\/pre>\n
\u539f\u59cb\u6570\u7ec4\u662f\uff1a\n[[ 0  5 10 15]\n [20 25 30 35]\n [40 45 50 55]]\n\u4ee5 C \u98ce\u683c\u987a\u5e8f\u6392\u5e8f\uff1a\n0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, \n\u4ee5 F \u98ce\u683c\u987a\u5e8f\u6392\u5e8f\uff1a\n0, 20, 40, 5, 25, 45, 10, 30, 50, 15, 35, 55, <\/code><\/pre>\n
\u4fee\u6539\u6570\u7ec4\u4e2d\u5143\u7d20\u7684\u503c<\/h3>\n
nditer<\/code> \u5bf9\u8c61\u6709\u53e6\u4e00\u4e2a\u53ef\u9009\u53c2\u6570 op_flags<\/code>\u3002 \u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0cnditer <\/code>\u5c06\u89c6\u5f85\u8fed\u4ee3\u904d\u5386\u7684\u6570\u7ec4\u4e3a\u53ea\u8bfb\u5bf9\u8c61\uff08read-only<\/code>\uff09\uff0c\u4e3a\u4e86\u5728\u904d\u5386\u6570\u7ec4\u7684\u540c\u65f6\uff0c\u5b9e\u73b0\u5bf9\u6570\u7ec4\u5143\u7d20\u503c\u5f97\u4fee\u6539\uff0c\u5fc5\u987b\u6307\u5b9a read-write<\/code> \u6216\u8005 read-only<\/code> \u7684\u6a21\u5f0f\u3002<\/p>\n
import numpy as np\na = np.arange(0,60,5) \na = a.reshape(3,4)  \nprint ('\u539f\u59cb\u6570\u7ec4\u662f\uff1a')\nprint (a)\nfor x in np.nditer(a, op_flags=['readwrite']): \n    x[...]=2*x \nprint ('\u4fee\u6539\u540e\u7684\u6570\u7ec4\u662f\uff1a')\nprint (a)\n# \u539f\u59cb\u6570\u7ec4\u662f\uff1a\n#[[ 0  5 10 15]\n# [20 25 30 35]\n# [40 45 50 55]]\n#\u4fee\u6539\u540e\u7684\u6570\u7ec4\u662f\uff1a\n#[[  0  10  20  30]\n# [ 40  50  60  70]\n# [ 80  90 100 110]]<\/code><\/pre>\n
\u4f7f\u7528\u5916\u90e8\u5faa\u73af<\/h3>\n
\"image-20220823214320745\"<\/div><\/p>\n
import numpy as np \na = np.arange(0,60,5) \na = a.reshape(3,4)  \nprint ('\u539f\u59cb\u6570\u7ec4\u662f\uff1a')\nprint (a)\nprint ('\u4fee\u6539\u540e\u7684\u6570\u7ec4\u662f\uff1a')\nfor x in np.nditer(a, flags =  ['external_loop'], order =  'F'):  \n   print (x, end=", " )\n# \u539f\u59cb\u6570\u7ec4\u662f\uff1a\n#[[ 0  5 10 15]\n# [20 25 30 35]\n# [40 45 50 55]]\n# \u4fee\u6539\u540e\u7684\u6570\u7ec4\u662f\uff1a\n#[ 0 20 40], [ 5 25 45], [10 30 50], [15 35 55], <\/code><\/pre>\n
\u5e7f\u64ad\u8fed\u4ee3<\/h3>\n
import numpy as np \na = np.arange(0,60,5) \na = a.reshape(3,4)  \nb = np.array([1,  2,  3,  4], dtype =  int)  \nfor x,y in np.nditer([a,b]):  \n    print ("%d:%d"  %  (x,y), end=", " )\n# 0:1, 5:2, 10:3, 15:4, 20:1, 25:2, 30:3, 35:4, 40:1, 45:2, 50:3, 55:4, <\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
Numpy\u9ad8\u7ea7\u7d22\u5f15 \u6574\u6570\u6570\u7ec4\u7d22\u5f15 import numpy as np x = np.array([[1, 2 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12,32],"tags":[],"class_list":["post-247","post","type-post","status-publish","format-standard","hentry","category-artificial-intelligence","category-python-learn"],"_links":{"self":[{"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/posts\/247","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/comments?post=247"}],"version-history":[{"count":2,"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/posts\/247\/revisions"}],"predecessor-version":[{"id":249,"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/posts\/247\/revisions\/249"}],"wp:attachment":[{"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/media?parent=247"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/categories?post=247"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/162.14.82.114\/index.php\/wp-json\/wp\/v2\/tags?post=247"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}