Python-functional programming (passing functions as parameters)

Map: Accepts two parameters (function, iterable), map passes the incoming function to each element of iterable, and returns the new iterable

def f (x):     return x*= map (f,[1,2,3,4])    # at this time R is lazy evaluation-can be used next () and for...in value # return all through list () Print (List (R))  # [1, 4, 9, +]

Reduce: Accepts two parameters (function, sequence), reduce takes a function on a sequence, and the returned result continues to accumulate with the next element of the sequence, with the effect of: reduce (F,[x,y,z]) =>f (f (x, y), z)

 from Import Reduce def Add (x, y    ): return x+yreduce (add,[#

Filter: Filter sequence. Accept two parameters (function, sequence), filter to function on the sequence, depending on whether the return value is true, decide whether to discard the element

def is_odd (x):     return x%2==1list (filter (is_odd,[1,2,3,4,5,6,7,8,9))    #Filter Lazy evaluation [1, 3, 5, 7, 9]

Sorted: Sort, sortable objects include number list, string list, dict, etc., can accept three parameters, the latter two are optional

# sorted ([],key=express,reverse=true) key: How to handle each element   reverse: Reverse sort #[8, 6, 3,-2, 1,-1, 0] 

Anonymous FunctionsLambda: anonymous function keyword: The preceding element represents the parameter of an anonymous function anonymous function without thanking the return expression, the return value is the value of the expression

m = List (map (Lambda x:x*x,[1,2,3,4))print(m)    #[1, 4, 9, +]

Decorative Device: Dynamically increasing functionality during code run

#automatically print logs before the now function runsImportFunctoolsdeflog (func): @functools. Wraps (func)defWrpper (*args,**kw):Print("Call %s ()"% func.__name__)        returnFunc (*args,**kw)returnWrpper#Call Adorner@logdefNow ():Print("Hello") Now ()#Call Now () Hello

Partial function: functools.partial Fixed some parameters of the function, returning a new function to make the call simpler

Import= functools.partial (int,base=2)print(Int2 ("1000000" ))  #

Python-functional programming (passing functions as parameters)