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[英]Concatenate/stack unpacked numpy array in certain axis to other arrays
[英]Concatenate arrays with stack numpy
import numpy as np
t = np.arange(3)
for i in range(5):
a = np.arange(3)
np.stack((t, a))
print(t)
output = [0 1 2]
请帮忙在循环中连接 arrays for,ty!
import numpy as np
t = np.arange(3)
for i in range(5):
a = np.arange(3)
t = np.vstack((t, a))
print(t)
Output:
[[0 1 2]
[0 1 2]
[0 1 2]
[0 1 2]
[0 1 2]
[0 1 2]]
请注意,避免 for 循环会执行相同的任务
nx,ny = 5,5
快 5 倍nx,ny = 50,50
快 31 倍nx,ny = 500,500
快 57 倍这里的代码:
import numpy as np
nx = 500; ny = 500
def f0():
t = np.arange(ny)
for i in range(nx):
a = np.arange(ny)
t = np.vstack((t, a))
return t
def f1():
o = np.ones(nx, dtype=int)
t = np.arange(ny)
return np.outer(o,t) # the outer product between 2 vectors
%timeit y0 = f0()
13.2 ms ± 1.35 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
%timeit y1 = f1()
229 µs ± 1.95 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
import numpy as np
t = np.arange(3)
for i in range(5):
a = np.arange(3)
t = np.concatenate((t, a))
print(t)
Output:
[0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2]
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