Substitution on Function Iteration

[Scott Guthery]

Any insight into the following will be greatly appreciated.  Many thanks.

from sympy import *

x = symbols('x', integer=True)

def main(fns, q0):

    for fn in fns:

        print(fn)

        print(fn.subs([x,q0]))

    

if __name__ == '__main__':

    f1=x

    f2=x+2

    main([f1,f2], 3)

yields

x

Traceback (most recent call last):

  File ".../Subs.py", line 13, in <module>

    main([f1,f2], 3)

  File ".../Subs.py", line 8, in main

    print(fn.subs([x,q0]))

  File "C:\Python34\lib\site-packages\sympy\core\basic.py", line 842, in subs

    o, n = sequence[i]

TypeError: 'Symbol' object is not iterable

[Sudhanshu Mishra]

Hi Scott,

It looks like your subs call is wrong. It should be fn.subs(x, q0)

Hope this helps.

Sudhanshu Mishra

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[Aaron Meurer]

The argument to subs should either be subs(old, new), or an iterable
of (old, new) pairs, so subs(x, q0) or subs([(x, q0)]) (you can also
pass in a dictionary like subs({x: q0})).

Aaron Meurer

> https://groups.google.com/d/msgid/sympy/CAFW_KCR2DpZKsWXuWJYW%3Dpwo1AsJf6sgCHbM0%3D%2BbfTMwF7bkLA%40mail.gmail.com.

[Scott Guthery]

Yep.  Thanks much, Sudhanshu

Cheers, Scott