NumPy详细API第一篇

以下代码是基于python3.5.0写的 import numpy # 读取文件内容 world_alcohol = numpy.genfromtxt("world_alcohol.txt", delimiter=",",dtype="float",skip_header=1) print(type(world_alcohol)) print(world_alcohol) vector = numpy.array([1, 2, 3, 4]) #构造数组 print(vector.shape) #打印数组形状 matrix = numpy.array([[5, 10, 15], [20, 25, 30]]) #构造矩阵 print(matrix.shape) #打印矩阵形状 numbers = numpy.array([1, 2, 3, 4]) # 查看数组中元素类型 print(numbers.dtype) uruguay_other_1986 = world_alcohol[1,4] # 读取第1行第4个元素 third_country = world_alcohol[2,2] # 读取第2行第2个元素 vector = numpy.array([5, 10, 15, 20]) print(vector[0:3]) # 查找数组前三个值 matrix = numpy.array([ [5, 10, 15], [20, 25, 30], [35, 40, 45]]) print(matrix[:,1]) # ：代表所有的意思，查找所有行第一列的值[10 25 40] matrix = numpy.array([ [5, 10, 15], [20, 25, 30], [35, 40, 45]]) print(matrix[:,0:2]) # 查找所有行，前两列的值[[ 5 10]，[20 25]，[35 40]] matrix = numpy.array([ [5, 10, 15], [20, 25, 30], [35, 40, 45]]) print(matrix[1:3,0:2]) # 查找2到3行，前两列的值[[20 25]，[35 40]