在python中导入一个数组

Question

如何从文件中将数组导入python(numpy.arry),如果文件尚不存在,则必须写入该文件.

例如,将矩阵保存到文件然后加载回来.

Answer 1

签出numpy示例列表中的条目.这是.loadtxt()上的条目

>>> from numpy import *
>>>
>>> data = loadtxt("myfile.txt")                       # myfile.txt contains 4 columns of numbers
>>> t,z = data[:,0], data[:,3]                         # data is 2D numpy array
>>>
>>> t,x,y,z = loadtxt("myfile.txt", unpack=True)                  # to unpack all columns
>>> t,z = loadtxt("myfile.txt", usecols = (0,3), unpack=True)     # to select just a few columns
>>> data = loadtxt("myfile.txt", skiprows = 7)                    # to skip 7 rows from top of file
>>> data = loadtxt("myfile.txt", comments = '!')                  # use '!' as comment char instead of '#'
>>> data = loadtxt("myfile.txt", delimiter=';')                   # use ';' as column separator instead of whitespace
>>> data = loadtxt("myfile.txt", dtype = int)                     # file contains integers instead of floats

Answer 2

另一种选择是numpy.genfromtxt,例如:

import numpy as np
data = np.genfromtxt("myfile.dat",delimiter=",")

这将生成data一个numpy数组,其中包含与文件一样多的行和列