ExampleEdit & Run
#Using the map Function

def square(n):
    return n * n


L = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
map_object = map(square, L) #Get the  of square of each value of list L

print(list(map_object)) #Convert the map object into a list
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Output:
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
[Finished in 0.010963517241179943s]

The map() function applies a given function to each item of an iterable object. It returns an iterator object containing the transformed element as per the given function. 

Syntax: 
map(key, iterable)
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key A required argument that specifies the function that will be applied to all the elements of the iterable.
iterable The iterable whose each element will be passed to the key function.
Parameters:

The map() function returns a map object containing the return values by the function after being applied to each item of the iterable. The map object is iterable  and can be casted to other collection data types such as list, tuple, set, etc.

For example if we want to turn all the elements of an iterable to integers, we can pass the built-in int function.

ExampleEdit & Run
map_obj = map(int, [1.0, 2.0, 3.0, 4.0, 5.0])

print(map_obj)
print(list(map_obj))
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Output:
<map object at 0x7f497d513e80>
[1, 2, 3, 4, 5]
[Finished in 0.009446178562939167s]

The decision whether to use the map function or  loops  depends on the specific task. Generally speaking, the map function is typically used for simple  operations and transformations, while loops are used for more complex operations. 

The following example illustrates solving a task with loops and solving the same task using map().

ExampleEdit & Run

using while loop 

L = ['0.1', '0.15', '0.2', '0.25', '0.3']

i = 0
while i< len(L):
   L[i] = float(L[i])
   i += 1

print(L)

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Output:
[0.1, 0.15, 0.2, 0.25, 0.3]
[Finished in 0.009777389466762543s]
ExampleEdit & Run

using for loops

L = ['0.1', '0.15', '0.2', '0.25', '0.3']

for i,v in enumerate(L):
    L[i] = float(v)

print(L)
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Output:
[0.1, 0.15, 0.2, 0.25, 0.3]
[Finished in 0.009695310145616531s]
ExampleEdit & Run

Using map() function

data = ['0.1', '0.15', '0.2', '0.25', '0.3']

L = list(map(float, data))

print(L)
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Output:
[0.1, 0.15, 0.2, 0.25, 0.3]
[Finished in 0.009101842530071735s]

Let us see few more practical examples of using map().

ExampleEdit & Run
print( list(map(int, ['1', '2', '3', '4', '5', '6'])) ) #turn strings to integers

print( list(map(len, [[1, 2], [], [3, 4, 5], [1], [7,8]])) ) #get the length of each inner list

print( list(map(lambda x: x*x, [i for i in range(10)])) ) # square range values 

print( list(map( lambda name : ' '.join(name), [('John', 'Doe'), ('Jane','Doe'), ('Will', 'Smith')])) ) #concatenate strings 

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Output:
[1, 2, 3, 4, 5, 6]
[2, 0, 3, 1, 2]
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
['John Doe', 'Jane Doe', 'Will Smith']
[Finished in 0.009949389845132828s]