SymPy Gamma

Input:

(exp(x) / (1 + exp(2x))).subs(exp(x), u)

Error:

(exp(x) / (1 + exp(2x))).subs(exp(x), u)

can't multiply sequence by non-int of type 'method'

See what Wolfram|Alpha has to say.

Experiment with SymPy at SymPy Live.