## Question

Asked By – Kyle Heuton

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 us 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?

**Now we will see solution for issue: How do I find the length (or dimensions, size) of a numpy matrix in python? [duplicate] **

## Answer

`shape`

is a property of both numpy ndarray’s and matrices.

```
A.shape
```

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

In fact, the numpy `matrix`

object is built on top of the `ndarray`

object, one of numpy’s two fundamental objects (along with a universal function object), so it inherits from `ndarray`

This question is answered By – Kyle Heuton

**This answer is collected from stackoverflow and reviewed by FixPython community admins, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 **