从字面上呈现一个表达式，没有简化

Question

I wonder how I can make sympy behave such that the expression is rendered literally and no defactoring occurs (4 under the sqrt)

from sympy import init_session
init_session(quiet=true)
from sympy.interactive import printing
printing.init_printing(use_latex=True)
a=sqrt(4*A**2*Z**2)
a

gives

2 * sqrt(a**2*Z**2)

I'd rather would have it written as initially written (in the course of an educational text). So how does one prevent sympy from doing any simplifications or resolving?

Answer 1

Use an "evaluate(False)" block to stop the simplifaction/evaluation rules:

(I am using Python 3.4, sympy 0.7)

with evaluate(False):
    print(sqrt(4*x))

sqrt(4*x)
>>>

Answer 2

As of now, there is no way to do this with sympy. It parses the input sqrt(4*A**2*Z**2) and stores the expression tree, along the way sorting the terms as it sees fit, combining all rational factors into one, etc. There is no information left about the original input.

Reference: Issue #3846: Allow manipulation of raw expression trees , which was open in 2008. The issue does not appear likely to be resolved any time soon.