Out of the 577 existing constituencies, there are: Moreover, the French Constitution sets the maximum number of MPs at 577.
Legislative elections need to be held during the 60-day period preceding the expiration of the outgoing Assembly's powers.
Besides, per the French Constitution (article 12), the President has the power to dissolve the National Assembly after consulting with the Prime minister and the heads of the lower and upper houses of Parliament.
The Constitution does not set limits on that power apart from prohibiting another dissolution from occurring less than a year after the last one.
It was the first snap election since 1997 when President Jacques Chirac dissolved the National Assembly a year early.