Description map()

Python map()

The map() function applies a given function to each item of an iterable (list, tuple etc.) and returns a list of the results.

The syntax of map() is:
map(function, iterable, ...)

map() Parameter

• function - map() passes each item of the iterable to this function.
• iterable iterable which is to be mapped
You can pass more than one iterable to the map() function.

Return Value from map()

The map() function applies a given to function to each item of an iterable and returns a list of the results.
The returned value from map() (map object) then can be passed to functions like list() (to create a list), set() (to create a set) and so on.

Example 1: How map() works?

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def calculateSquare(n):
return n*n

numbers = (1, 2, 3, 4)
result = map(calculateSquare, numbers)
print(result)

# converting map object to set
numbersSquare = set(result)
print(numbersSquare)
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When you run the program, the output will be:
<map object at 0x7f722da129e8>
{16, 1, 4, 9}In the above example, each item of the tuple is squared.

Since map() expects a function to be passed in, lambda functions are commonly used while working with map() functions.
A lambda function is a function without a name.

Example 2: How to use lambda function with map()?

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numbers = (1, 2, 3, 4)
result = map(lambda x: x*x, numbers)
print(result)

# converting map object to set
numbersSquare = set(result)
print(numbersSquare)
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When you run the program, the output will be:
<map 0x7fafc21ccb00>
{16, 1, 4, 9}There is no difference in functionalities of this example and Example 1.

Example 3: Passing Multiple Iterators to map() Using Lambda

In this example, corresponding items of two lists are added.
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num1 = [4, 5, 6]
num2 = [5, 6, 7]

result = map(lambda n1, n2: n1+n2, num1, num2)
print(list(result))
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When you run the program, the output will be:
[9, 11, 13]