Q:

How do I display a full expression in sympy?

I am trying to use sympy in a Jupyter notebook to document and perform a series of mathematical cacluations in a reporducible way.
If I define the following:
from sympy import *

init_printing()
x, y, z = symbols("x y z")

x=y+z
x

then I can display the value of x (that is, y+z).
How do I display the full equation (x=y+z)?
Running Eq(x,y+z), even with evaluate=False) returns the expression with the value of x substituted (y+z=y+z).

A:

Although you first declare x as a sympy.Symbol, once you perform the assignment x=y+z, x becomes an alias for y+z. Whenever you use x from that point after, x will be automatically translated by python as y+z. 
If you insist on this workflow, you could use Eq(S('x'),y+z) to display the equation.

