Yichuan Wang - 6 months ago 32

Python Question

I know that numpy array has a method called shape that returns [No.of rows, No.of columns], and shape[0] gives you the number of rows, shape[1] gives you the number of columns.

`a = numpy.array([[1,2,3,4], [2,3,4,5]])`

a.shape

>> [2,4]

a.shape[0]

>> 2

a.shape[1]

>> 4

However, if my array only have one row, then it returns [No.of columns, ]. And shape[1] will be out of the index. For example

`a = numpy.array([1,2,3,4])`

a.shape

>> [4,]

a.shape[0]

>> 4 //this is the number of column

a.shape[1]

>> Error out of index

Now how do I get the number of rows of an numpy array if the array may have only one row?

Thank you

Answer

The concept of *rows* and *columns* applies when you have a 2D array. However, the array `numpy.array([1,2,3,4])`

is a 1D array and so has only one dimension, therefore `shape`

rightly returns a single valued iterable.

For a 2D version of the same array, consider the following instead:

```
>>> a = numpy.array([[1,2,3,4]]) # notice the extra square braces
>>> a.shape
(1, 4)
```