Numpy

Arrays

Initializing an empty array

Sometimes you want to initalize an empty array, which is a really inefficient use of memory for large matrices but you could care less if it's a dozen items.

# You can initialize an array with []: 

In [62]: x=[]

In [63]: x=np.array(x)

In [64]: x
Out[64]: array([], dtype=float64)

# to be more direct about it,

In [66]: x = np.array([],dtype=np.float64)

In [67]: x
Out[67]: array([], dtype=float64)

# Now you can append to the empty array

In [71]: x = append(x,1)

In [72]: x = append(x,2)

In [73]: x=append(x,3)

In [74]: x
Out[74]: array([ 1.,  2.,  3.])