Map in python.

Question

please explain about map function in Python and what is the use of it?

Answer 1

4.1. Map

Map applies a function to all the items in an input_list. Here is the blueprint:

Blueprint

map(function_to_apply, list_of_inputs)

Most of the times we want to pass all the list elements to a function one-by-one and then collect the output. For instance:

items = [1, 2, 3, 4, 5]
squared = [] for i in items: squared.append(i**2)

Map allows us to implement this in a much simpler and nicer way. Here you go:

items = [1, 2, 3, 4, 5]
squared = list(map(lambda x: x**2, items))

Most of the times we use lambdas with map so I did the same. Instead of a list of inputs we can even have a list of functions!

def multiply(x): return (x*x) def add(x):
return (x+x)
funcs = [multiply, add] for i in range(5):
value = list(map(lambda x: x(i), funcs)) print(value) # Output: # [0, 0] # [1, 2] # [4, 4] # [9, 6] # [16, 8]

http://book.pythontips.com/en/latest/map_filter.html