In one of the previous posts, we showed you how to work with in-line *Python* functions directly in STRUREL. Did you know? You can also use a *Python* script as limit-state function in STRUREL.

Again, we use the example limit-state function *R*–*S* that we already used in the past: Our stochastic model consists of the two random variables *R* and *S*, where *R* represents the resistance of a system of interest and *S* is the system load. The *symbolic expression* for the corresponding limit-state function in the native syntax of STRUREL would be:

`FLIM(1) = R-S`

However, if you have *Python* installed on your system and if the *Python* interface of STRUREL is configured correctly, you could also use the following expression:

`FLIM(1) = pythons("my_model")`

where `my_model.py`

is a *Pyhton* script file located in the same directory as the iti-file of STRUREL.

For the example at hand, the *Python* script file should look as follows:

`res = R - S`

where the variable names `R`

and `S`

must match the names of the random variables of the *stochastic model* of STRUREL. The variable `res`

must contain the value of the limit-state function, where the value of `res`

is later retrieved by STRUREL.

By means of the STRUREL command `pythons`

, you can integrate any limit-state function written in *Python* directly in your reliability analysis performed with STRUREL.