python, map, reduce, filter, custom sorting function, function and partial function decorator

import functools
from functools import reduce

# Map () is built python higher order function, a receiving function and a function list
 # sequentially to the function f acts on each element of the list to obtain a new list and returns.
Example # 1 each element of the list and returns the square do
 DEF F (X):
     return X * X

Print ( List ( Map (F , [ . 1 , 2 , . 3 , . 4 , . 5 ])))
 Print ( List ( Map ( the lambda X: X * X , [ . 1 , 2 , . 3 , . 4 , . 5 ])))   # anonymous function using the lambda
 # Note: because the list can contain any type of element, so that map () can not only handle the list contains values
 # list may further comprise any type of process, as long as the function f can be passed to process the data type
 # reduce () function is also built python higher-order functions, received parameters and map () is similar to a function f and a list, but behaves differently
 # reduce incoming f must receive two parameters, each element of a list of repeatedly calling the function f, and returns the final result value


Example # 1 for all the elements of the list are summed
 DEF F (X , Y):
     return X + Y

reduce(f, [1, 2, 3, 4, 5])

# May also receive the reduce the optional third parameter, as the calculation of the initial value
 # 2 Example summing all elements in list, and add 100
 DEF F (X , Y):
     return X + Y

reduce(f, [1, 2, 3, 4, 5], 100)


# Filter functions are built python Another useful higher order function, it receives a function f and a list, the determination function f for each element
 # returns True or False, filter to automatically filter out according to the determination result does not meet the conditions element, and returns the elements eligible new list
 # 1 is deleted from the list in the embodiment even, odd retained
 DEF isOdd (X):
     return X% 2 == . 1
 filter (isOdd , [ . 1 , 2 , . 3 , . 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ])


# None Example 2. Remove empty string or
 DEF isNotEmpty (S):
     return S and len (s.strip ())> 0
 filter (isNotEmpty , [ 'Test' , None, '' , '' ])



# Sort () is a higher order function, a comparison function may be received to implement custom ordering, comparison function is defined: Comparison with passing two elements X, Y
 # if x <y returns -1, x> y returns 1, x = y 0 is returned
 # Example 1. sort list
 the sorted ([ . 3 , . 6 , 2 , . 7 , 38 is , . 9 ])
 # 2. Example if we are to achieve reverse sort, only a write their own reversedCmp function
 DEF reversedCmp (X , Y):
     IF X> Y:
         return - . 1
 IF X <Y:
         return . 1
 return 0
 # the sorted ([5,3,6,4,1,7], reversedCmp) does not have to python3 # support the
 Print ( sorted ([ 'Bus'        
,'amount','Zero','Ceiling'], key=None))


# Decorator
 DEF fprint (F): # decorator function
 DEF Fn (X):
         Print ( 'Call' + F. The __name__ + "()" )
         return F (X)
     return Fn    

def f1(x):
    return x * x

F1 = fprint # (F1)
 # equivalent
 @fPrint
 DEF F1 (X):
     return X * X

Print (f1. __name__ )   # can see the function name is not 'f1', but 'fn' @fPrint internally defined
 # So for those who rely on the code name of the function will fail, and decorator also changes the function of __doc_ _ other property
 # If you want the caller can not see through the @decorator a function of "reform", you need to copy some of the attributes of the original function to a new function
 DEF fprint (f): # decorator function
 @functools. Wraps (F)
     DEF Fn (X):
         Print ( 'Call' + F. the __name__ + "()" )
         return F (X)
     return Fn
 @fPrint
 DEF F1 (X):
     return X * X
 Print (F1. the __name__ )      Such function name becomes # 'f1' the
 Print (F1 ( 2 ))
 int ( '1010101' )   # default decimal
 INT2 functools.partial = ( int , Base = 2 )   new parameter set # using the partial function of binary function
 INT2 ( '1010101' )