Modifying a part of the expression tree

[Bla Binorbit]

Hello,

I would like to modify a part of an expression so as to obtain:
`EXPR.args[2].args[1] = MODIFIED_SUB_EXPRESSION`

How can I do this? The elements returned by "args" are immutable tuples, I cannot edit them in place and I don't know how to create a modified copy.

Thank you for your help,

Olivier

[Chris Smith]

This is what `epath` is made for, I believe. I have not spent enough time with it to provide much help, however -- only a pointer.

/c

[Bla Binorbit]

Thank you. I didn't know `epath()`. Indeed, the following command performs the desired modification:
`epath("/[2]/[1]", EXPR, lambda expr: MODIFIED_SUB_EXPRESSION)`
Best regards,
Olivier