Use of zip/enumerate/map function

zip function

zip Function to package multiple iteratible objects , If the number of iteratible objects is different , Take the least .zip Unpacking is also a zip type , Need to cast to list or tuple type , The element after strong conversion is of tuple type

example ：

pack

#  Package into a list 
li1 = ['a', 'b', 'c']
li2 = [1, 2, 3]
res = list(zip(li1, li2))

print(type(res))
print(res)


#  Pack it up as a dictionary 
li1 = ['a', 'b', 'c']
li2 = [1, 2, 3]
res = dict(zip(li1, li2))

print(type(res))
print(res)

example 2：

Unpack

#  Unpack list 
li1 = ['a', 'b', 'c']
li2 = [1, 2, 3]
res = list(zip(li1, li2))

print(type(res))
print(res)

print(' The following result is unpacking '.center(50, '*'))

res2 = list(zip(*res))
print(type(res2))
print(type(res2[0]))        #  First element 
print(res2)

#  Unpacking dictionary 
li1 = ['a', 'b', 'c']
li2 = [1, 2, 3]
res = dict(zip(li1, li2))       #  Pack it up as a dictionary 

print(type(res))
print(res)

print(' The following result is unpacking '.center(50, '*'))

res2 = list(zip(*res.items()))       #  adopt items(), Turn the dictionary into a tuple of key value pairs , Then install it and replace it with list
print(type(res2))
print(type(res2[0]))        #  First element 
print(res2)

enumerate function

He can transform an iteratable object into a enumerate object , Generally used for subscript , The default from the 0 Start

grammar ：

enumerate( Iteratable object ,  Starting position )

example ：

li1 = ['a', 'b', 'c']
for key, val in enumerate(li1, 10):		#  The default from the 0 Start , Specify from  10  Start 
    print(key, val)

map function

Traversing an iteratable object , Pass each element into a function for processing

grammar ：

map( Function name ,  Iteratable object )

example ：

li = [3, 4, 9]


def func(x):
    return x ** 2


res = list(map(func, li))
print(res)

#  Using anonymous functions 
li = [3, 4, 9]
res = list(map(lambda x: x ** 2, li))
print(res)