CODEWITHSUNDEEP
pythonsymbolssympy
hola
hola

Reputation: 950

Declarating multiple symbolic variables in Python

When I declare a single symbolic variable, it works:

>>> from sympy import var
>>> x = var('x')
>>> x + 2
x + 2

Now, for my purpose I need multiple variables, say, s0, s1, ..., s9 and I also need operations like s0 + 1, s2 - s1 etc.

What will be the code? This will not work for me (EDIT: I mean I can do that, yeah, but for that I need to change my existing code a lot):

>>> from sympy import symbols
>>> s = symbols('s0:9'); s
(s0, s1, s2, s3, s4, s5, s6, s7, s8)
>>> s[0] + 1
s0 + 1

EDIT2: s0, s1, s2, s3, s4, s5, s6, s7, s8, s9 = symbols('s0:10') is fine, but the number of variables is not fixed.

Upvotes: 1

Views: 4126

Answers (2)

asmeurer
asmeurer

Reputation: 91620

First off, you should use symbols instead of var. var does some magic to inject the Symbols into the namespace, and should only be used interactively.

If you want an arbitrary number of Symbols, you want the numbered_symbols function, which produces an iterator. Here is the documentation. An example

>>> N = numbered_symbols('s')
>>> for s, _ in zip(N, range(10)):
...     print(s)
s0
s1
s2
s3
s4
s5
s6
s7
s8
s9

Upvotes: 3

Rushy Panchal
Rushy Panchal

Reputation: 17552

This works just fine, not sure what problem you are having with this:

>>> from sympy import symbols
>>> s = symbols('s0:10')
>>> s
(s0, s1, s2, s3, s4, s5, s6, s7, s8, s9)
>>> s[0] + 1
s0 + 1

If you want to set each to a variable, you can use multiple-assignment:

s0, s1, s2, s3, s4, s5, s6, s7, s8, s9 = symbols('s0:10')

This would be the equivalent of:

s0, s1 = Symbol('s0'), Symbol('s1') # and s2:s9 as well

Upvotes: 1

Related Questions