How to allow user input only if certain requirements are met

[vininhosts]

Im quite new to python. Sorry if I am too dumb.

I've been trying to build an agenda for a school, where classes can be scheduled only if other classes arent scheduled at that same time. What function should I attach to the variable, which in this case is the time?

[Larz60+]

what have you tried?

[vininhosts]

I have tried .find(), even though I am not sure what it does

[micseydel]

If you post the code you tried, we can give feedback on how to improve it.