List generators aka list comprehensions and list displays provide a quick way to create a list with selected elements from any enumerable object.
List generators are defined through the following syntaxes:
[element for item in enumerable] [element for item in enumerable if condition] [element for item in enumerable unless condition]
Some examples will help ilustrate the concept:
List with all the doubles from 0 to 5 (exclusive)
doubles = [i*2 for i in range(5)]
List with the names of the customers based on Rio de Janeiro
rjCustomers = [customer.Name for customer in customers if customer.State == "RJ"]