python中area是什么意思,从python中的2D数组中选择'area'

Is there a way to select a particular 'area' of a 2d array in python?

I can use array slicing to project out only one row or column but I am unsure about how to pick a 'subarray' from the large 2d array.

Thanks in advance

Jack

解决方案

If you are using the numpy library, you can use numpy's more advanced slicing to accomplish this like so:

import numpy as np

x = np.array([[1, 2, 3, 4],

[5, 6, 7, 8],

[9, 10, 11, 12]])

print x[0:2, 2:4]

# ^^^ ^^^

# rows cols

# Result:

[[3 4]

[7 8]]

(more info in the numpy docs)

If you don't want to use numpy, you can use a list comprehension like this:

x = [[1, 2, 3, 4],

[5, 6, 7, 8],

[9, 10, 11, 12]]

print [row[2:4] for row in x[0:2]]

# ^^^ ^^^ select only rows of index 0 or 1

# ^^^ and only columns of index 2 or 3

# Result:

[[3, 4],

[7, 8]]