map function

• A standard function that accepts at least 2 arguments: function and an “iterable”
  • functions: usually lambda functions
  • iterables: list, strings, dictionaries, sets, tuples
• Runs the function/lambda for each value in the iterable and returns a map object which can be converted into another data structure

nums = [1,2,3,4]
double = map(lambda x : x * 2, nums)
print(double) # <map object at 0x7f892b82e470> (a map object)
print(list(double)) # [2,4,6,8]
 
# same thing
double = list(map(lambda x : x * 2, nums))

• Can only be iterated once!!
  • so if you make it a list again and print, its an empty list

Examples

#getting only first names in a list
names = [
	 { 'first':'Leejun','last':'Kim' },
	 { 'first':'Kirby','last':'Yoshi'}
]
# lambda -> for every name, return the first name only 
first_names = list(map(lambda x: x['first'],names))
 
# decrememting each number in list
def decrement_list(nums):
    return list(map(lambda x:x-1, nums)) # [0,1,2]
decrement_list([1,2,3])