Hi and thanks both for your replies. xreplace doesn't look like
something I'd be interested in using, but as a very superficial
approximation, it looks like replace changes the expression
lexicographically but subs changes the expression mathematically. I
know I know that's *very* superficial but I
>
> (BTW as an aside, in some places in the documentation like p 502 (508
> of PDF) what is apparently a terminal transcript such as ">>> from
> sympy.matrices import" etc are not properly formatted -- just thought
> I'd mention.)
>
>
>>> eq=x+y+2
>>> eq.replace(x+1, z)
x + y + 2
>>> eq.subs(x+1, z
subs finds all instances of an expression and tries to replace them.
It takes into account mathematical knowledge (e.g., (4*x).subs(2*x, y)
will work, even though strictly speaking, 2*x is not part of the
expression tree of 4*x).
replace uses several methods to let you do more advanced substitutio
Hello again. Here's another question:
The documentation says that replace replaces "matching subexpressions
of self with value" and subs does "substitution of subexpressions as
defined by the objects themselves".
Unfortunately I am not totally able to comprehend the difference
between the two. Ca
