Python map function

describe:

map() will map the specified sequence according to the provided function.

The first argument function calls the function function with each element in the argument sequence, returning a new list containing the return value of each function function.

grammar:

map(function, iterable,...) 

• function – the function, with two arguments
• iterable -- one or more sequences

return value

Python 2.x returns a list.

Python 3.x returns iterators.

 

One, define a list

num_1 = [ 1, 2, 10, 5, 3, 7]

 implements each value multiplied by 2

num_1 = [1,2,10,5,3,7]
# ret = []
# for i in num_1:
#     ret.append(i**2)
# print (ret)

So now to achieve such a demand, it may be to add 1, it may be subtracted by 1, or it may be squared

num = [1,2,3,4]
def add_one(x):
      reture x+1
def reduce_one(x):
      return x-1
def map_test(func,array):
     ret = []
     for i in array:
         res = func(i)
         ret.append(res)
     return right
 #You can perform various operations you want to perform directly in the printout section
print(map_test(add_one,num))    
print(map_test(reduce_one,num))  

 The above method defines the addition and subtraction operation functions separately, which is not concise enough. The more concise way of writing is as follows: (the output is directly written by an anonymous function)

num = [1,2,3,4]
def map_test(func,array):
     ret = []
     for i in array:
         res = func(i)
         ret.append(res)
     return right
 #You can perform various operations you want to perform directly in the printout section
print(map_test(lambda x:x+1,num))    
print(map_test(lambda x:x-1,num))  

 Final version: handle with map function

print list(map(lambda x:x+1,num_1))