How to iterate over columns of a matrix?
Question:
In python if a define:
a = arange(9).reshape(3,3)
as a 3×3 matrix and iterate:
for i in a:
It’ll iterate over the matrix’s rows. Is there any way to iterate over columns?
Answers:
How about
for i in a.transpose():
or, shorter:
for i in a.T:
This may look expensive but is in fact very cheap (it returns a view onto the same data, but with the shape and stride attributes permuted).
Assuming that a is a well formed matrix, you could try something like:
b = zip(*a)
for index in b:
...
In python if a define:
a = arange(9).reshape(3,3)
as a 3×3 matrix and iterate:
for i in a:
It’ll iterate over the matrix’s rows. Is there any way to iterate over columns?
How about
for i in a.transpose():
or, shorter:
for i in a.T:
This may look expensive but is in fact very cheap (it returns a view onto the same data, but with the shape and stride attributes permuted).
Assuming that a is a well formed matrix, you could try something like:
b = zip(*a)
for index in b:
...