Three higher-order functions

1. map 与reduce

   • map()

     • Prototype map (fn, lsd)

       • 1 is a function of the parameter

       • 2 is a list of parameters

     • Features

       • The functions passed successively to each element in the sequence, and to return the result as a new Iterator

   • reduce()

     • Need to import from functools import reduce

     • Prototype reduce (fn, lsd)

       • 1 is a function of the parameter

       • 2 is a list of parameters

     • Function: a function of acting on the sequence, this function must accept two parameters, and the reduce the result of the next element in the sequence continues to cumulative operation

2. filter()

   • Prototype filter (fn, lsd)

     • 1 as a function parameter

     • 2 is a sequence parameter

   • Function: the sequence for filtering (filter data)

   • Vernacular: The function passed successively to each element of the sequence, according to returns True or False decide whether to keep the element

3. sorted()

   • Sort: bubble, choose quick sort, insert, counter

   • sorted(lsd,key=)

     • A parameter sequence

     • Parameters 2key to accept function to implement custom sorting rules

   • sorted(lsd,reverse = True)

     • A parameter sequence

     • Descending order parameter 2