function do not need define with no need of name
simple function with remove def, bracket and one line
# lambda input : output name = lambda parameters: function(parameters) name(argument)
usually used for functions (for collections)
key variable need function variable (lambda type is 'function')
- sort
collection.sort(key = len) collection.sort(key = lambda c:len(c))
- filter
# return new list of items which return function to true by item parameter filter(function, list)
- reduce