Back

Explore Courses Blog Tutorials Interview Questions
0 votes
1 view
in Python by (47.6k points)

For a numpy matrix in python

from numpy import matrix 

A = matrix([[1,2],[3,4]])

How can I find the length of a row (or column) of this matrix? Equivalently, how can I know the number of rows or columns?

So far, the only solution I've found is:

len(A) 

len(A[:,1]) 

len(A[1,:])

Which returns 2, 2, and 1, respectively. From this, I've gathered that len() will return the number of rows, so I can always use the transpose, len(A.T), for the number of columns. However, this feels unsatisfying and arbitrary, as when reading the line len(A), it isn't immediately obvious that this should return the number of rows. It actually works differently than len([1,2]) would for a 2D python array, as this would return 2.

So, is there a more intuitive way to find the size of a matrix, or is this the best I have?

1 Answer

0 votes
by (106k points)

To find the length of a numpy matrix in Python you can use shape which is a property of both numpy ndarray's and matrices.

A.shape

The above code will return a tuple (m, n), where m is the number of rows, and n is the number of columns.

If you are interested to learn Python from Industry experts, you can sign up for this Python Certification Course by Intellipaat.

Related questions

0 votes
1 answer
0 votes
1 answer
asked Jul 17, 2019 in Python by Sammy (47.6k points)
0 votes
1 answer
0 votes
1 answer
asked Oct 3, 2019 in Python by Sammy (47.6k points)
Welcome to Intellipaat Community. Get your technical queries answered by top developers!

28.4k questions

29.7k answers

500 comments

94k users

Browse Categories

...