lambdify of an empty matrix

[Felipe Bordeu]

Hello everyone,

I'm trying to use lambdify on some matrix expression, but my problem is that the shape of the matrix expr is not preserved. this is an example of my problem:

'''

from sympy import Symbol, Matrix

from sympy.utilities.lambdify import lambdify

xi  = Symbol("xi")

eta = Symbol("eta")

phi = Symbol("phi")

mat22 = Matrix([[xi+1,eta],[phi+2,eta]])

mat11 = Matrix([[xi+1]])

mat00 = Matrix([[]])

print("shape of the expression")

print(mat22.shape)

print(mat11.shape)

print(mat00.shape)

symbols = [xi,eta,phi]

args = [0,1,2]

print("shape of the lambdify expression")

print(lambdify(symbols,mat22)(*args).shape)

print(lambdify(symbols,mat11)(*args).shape)

print(lambdify(symbols,mat00)(*args).shape)

''

output: 

shape of the expretion

(2, 2)

(1, 1)

(0, 0)

shape of the lambdify expretion

(2, 2)

(1, 1)

(0,)                               <-----  i will like to have (0,0)

Any idea on how to solve this issue

using : 

Python 3.6.10 |Anaconda, Inc.| (default, May  8 2020, 02:54:21) 

[GCC 7.3.0] on linux

>>> sympy.__version__

'1.5.1'

Felipe

[Aaron Meurer]

This looks like a bug. Can you open an issue for it? The problem is
that it generates the code "array([])" for the empty matrix, but that
creates a shape (0,) array. It should instead use empty((0, 0)) to
create an empty array with the correct shape.

By the way, SymPy 1.5.1 is a relatively old version of SymPy. The
newest version is 1.7.1 (although this issue still persists even in
the git version).

Aaron Meurer

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