Continuing with a functional approach of python we take a look to the List functions. we will provide a little example for each one of this functions. This functions are map, reduce and filter.
Map
Map applies a function to each one of the elements of a sequence
secuence = list(range(0,10))
# secuence = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
f = lambda x: x + 1
map(f, secuence)
# result [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Filter
Filter reduces a secuence depending of a boolean function
secuence = list(range(0, 10))
# secuence = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
f = lambda x: x % 2 == 0
filter(f, secuence)
#result = [0, 2, 4, 6, 8]
Reduce
Reduce, is a operation that "reduces a list" apliying an operator
from functools import reduce
secuence = list(range(0, 10))
# secuence = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
f = lambda x, y: x + y
reduce(f,secuence)
# result = 45
# Using initial value, thanks to @magicleon94
reduce(f,secuence, 10)
# result = 55
Top comments (4)
An interesting thing you might point out is that
reducetakes an optional third parameter, which is an initial value. This could be useful in some situationI will add it to post, thanks!
Could you please explain statement ? I know
f = lambda x, y: x + y
is a function that add two numbers, i store it on a variable. You can use it with f(2, 1)