python - 在函数内连接 numpy 数组并返回它？

Question

考虑以下程序，如何在函数内连接两个 numpy 数组并返回它

#!/usr/bin/env python
import numpy as np

def myfunction(myarray = np.zeros(0)):
    print "myfunction : before = ", myarray    # This line should not be modified
    data = np.loadtxt("test.txt", unpack=True) # This line should not be modified
    myarray = np.concatenate((myarray, data))
    print "myfunction : after = ", myarray     # This line should not be modified
    return                                     # This line should not be modified

myarray = np.array([1, 2, 3])
print "main : before = ", myarray
myfunction(myarray)
print "main : after = ", myarray

这段代码的结果是:

main : before =  [1 2 3]
myfunction : before =  [1 2 3]
myfunction : after =  [ 1.  2.  3.  1.  2.  3.  4.  5.]
main : after =  [1 2 3]

我想要:

main : before =  [1 2 3]
myfunction : before =  [1 2 3]
myfunction : after =  [ 1.  2.  3.  1.  2.  3.  4.  5.]
main : after =  [ 1.  2.  3.  1.  2.  3.  4.  5.]

如何修改提供的程序以获得预期的结果(#This line should not be modified标记的4行应该保持不变)？

Answer 1

你应该返回值

像这样修改函数:

def myfunction(myarray = np.zeros(0)):
    print "myfunction : before = ", myarray    # This line should not be modified
    data = np.loadtxt("test.txt", unpack=True) # This line should not be modified
    concatenated = np.concatenate((myarray, data))
    print "myfunction : after = ", myarray     # This line should not be modified
    return  concatenated

然后你得到这样的结果

result = myfunction(myarray)