Python basic tutorial: How to use Map

Python Map

Map maps a function to all elements of an input list. The specification of Map is: map(function_to_apply, list_of_inputs)
Most of the time, we need to pass all the elements in the list to a function one by one and collect the output. For example:

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

Using Map allows us to solve this problem in a simpler way.

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

Most of the time, we will use the anonymous function lambda in python to cooperate with map. Not only for a list of inputs, but we can also use it for 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)

The output of the above program is:

# Output: 
# [0, 0] 
# [1, 2] 
# [4, 4] 
# [9, 6] 
# [16, 8]

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