Using Numpy Shape Output In Logic

I am using Python 2.7.5 on Windows 7. For some reason python doesn't like it when I use one of the dimensions of my numpy array to with a comparator in an if statement: a = np.arra

Solution 1:

You are creating a tuple with np.shape so you are passing (1,(4,)) so the error has nothing to do with your if, it is what is happening inside the if , you would need to use np.shape(a)[0] but I am not fully sure what you are trying t do:

 np.shape(a)[0]

Or simply a.shape[0]

Solution 2:

The problematic line is a = np.reshape(a, (1, np.shape(a))).

To add an axis to the front of a I'd suggest using:

a = a[np.newaxis, ...]

print a.shape # (1, 4)

or None does the same thing as np.newaxis.

Solution 3:

Looks like you are trying to do the same thing as np.atleast_2d:

defatleast_2d(*arys):   # *arys handles multiple arrays
    res = []
    for ary in arys:
        ary = asanyarray(ary)
        iflen(ary.shape) == 0 :
            result = ary.reshape(1, 1)
        eliflen(ary.shape) == 1 :  # looks like your code!
            result = ary[newaxis,:]
        else :
            result = ary
        res.append(result)
    iflen(res) == 1:
        return res[0]
    else:
        return res

In [955]: a=np.array([1,2,3,4])
In [956]: np.atleast_2d(a)
Out[956]: array([[1, 2, 3, 4]])

or it is a list:

In [961]: np.atleast_2d([1,2,3,4])
Out[961]: array([[1, 2, 3, 4]])

you can also test the ndim attribute: a.ndim==1