使用带“append”模式的open()，并将流传递给savetxt方法：

with open("test.txt", "ab") as f:
    numpy.savetxt(f, a)

编辑：添加新行或其他内容：

with open("test.txt", "ab") as f:
    f.write(b"\n")
    numpy.savetxt(f, a)

应在追加模式下打开该文件

import numpy as np        
f=open('file.txt','a')
a = np.array([1.2, 2.3, 4.5])
b = np.array([6.7, 8.9, 10.11])
c = np.array([12.13, 14.15, 16.17])
np.savetxt(f, a, fmt='%1.3f', newline=", ")
f.write("\n")
np.savetxt(f, b, fmt='%1.3f', newline=", ")
f.write("\n")
np.savetxt(f, c, fmt='%1.3f', newline=", ")
f.write("\n")
f.close()

实现行和换行符的更简单的方法。

import numpy as np

a = np.array([1.2, 2.3, 4.5])
b = np.array([6.7, 8.9, 10.11])
c = np.array([12.13, 14.15, 16.17])
      
with open('file.txt','a') as f:
    np.savetxt(f, a.reshape(1, -1), fmt='%1.3f', delimiter=",")
    np.savetxt(f, b.reshape(1, -1), fmt='%1.3f', delimiter=",")
    np.savetxt(f, c.reshape(1, -1), fmt='%1.3f', delimiter=",")

file.txt的内容（假设file.txt为空或不存在）

1.200,2.300,4.500
6.700,8.900,10.110
12.130,14.150,16.170

另外，请注意，如果您不是每次都重新打开文件，np.savetxt会有效地将b和c添加到现有文件中，因此您可以从一开始就使用写模式。不确定这是您想要的还是要附加到已经存在的文件中。

with open('file.txt', 'w') as f:
    np.savetxt(f, a.reshape(1, -1), fmt='%1.3f', delimiter=",")
    np.savetxt(f, b.reshape(1, -1), fmt='%1.3f', delimiter=",")
    np.savetxt(f, c.reshape(1, -1), fmt='%1.3f', delimiter=",")

（输出与上述相同，无论是否存在任何现有文件）