Transforming a list to a column vector in Python

Question

I was wondering if there\'s a function that takes a list X as input and outputs a column vector corresponding to X?

(I looked around and I susp

Answer 1

If you want to convert a Python list into a numpy column vector, you can use the ndmin argument to the array conductor:

col_vec = np.array(X, ndmin=2)

Simply constructing an array will give you a 1D array, which can not be directly transposed:

a = np.array(X)
a is a.T

There are a couple of ways to transform a 1D vector into a column though:

col_vec = a.reshape(-1, 1)

and

col_vec = a[np.newaxis, :]

are fairly common idioms after your list is already an array.

col_vec = np.reshape(X, (-1, 1))

and

col_vec = np.expand_dims(X, -1)

will work even on a raw list.

P.S. Stay away from np.matrix it's very outdated and limited, if not outright deprecated.