# [newbie] lambda operator

Can someone explain me the lambda operator. The first time I saw it was in this code fragment: pi = lambda x: pari(x).primepi()

I do understand pi(x) calculates the number of primes =< x but I don't understand the syntax used to accomplish this

thanks for having patience with a newbie jean

This was answered [here](https://groups.google.com/forum/#!topic/sage-support/alhml56_azc).

I like this explanation on Python Foundation page.