Answers for "column selection numpy matrix range"

python how to copy a 2d array leaving out last column

In [1]: import numpy as np

In [2]: H = np.meshgrid(np.arange(5), np.arange(5))[0]

In [3]: H
Out[3]: 
array([[0, 1, 2, 3, 4],
       [0, 1, 2, 3, 4],
       [0, 1, 2, 3, 4],
       [0, 1, 2, 3, 4],
       [0, 1, 2, 3, 4]])

In [4]: Hsub = H[1:-1,1:-1]

In [5]: Hsub
Out[5]: 
array([[1, 2, 3],
       [1, 2, 3],
       [1, 2, 3]])

how get 1st column in all rows of a 2d matrix in python

data = [
['a', 1, 2], 
['b', 3, 4], 
['c', 5, 6]
]

columns = list(zip(*data))

print("column[0] = {}".format(columns[0]))
print("column[1] = {}".format(columns[1]))
print("column[2] = {}".format(columns[2]))

# output
>>> print("column[0] = {}".format(columns[0]))
column[0] = ('a', 'b', 'c')

>>> print("column[1] = {}".format(columns[1]))
column[1] = (1, 3, 5)

>>> print("column[2] = {}".format(columns[2]))
column[2] = (2, 4, 6)