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WHAT ARE MAP, FILTER AND REDUCE FUNCTIONS IN PYTHON…
Sulochana Kamshetty
a year ago
Table of Content
- What is map()function in python
- The filter() Function
- Output
- Explanation
- The reduce() Function
- output
Welcome to the new article from insideAIML which gives the complete knowledge or clear understanding about
these above-mentioned topics.. those are
- Map
- Filter
- Reduce
Let us understand
these topics individually with the help of examples..
Map, Filter, and Reduce are language of functional
programming. They allow the programmer (you) to write simpler, shorter code
which is easy to understand and more feasible to code..
What is map()function in python:-
This simple map() function allows the programmer to
acces for many additional functions with simple codes which are iterables as
many times we apply it on..
Where func is the function on which each element is iterables (as many as they are) would be applied on.
The difference of python programmed which is In Python2
version, the map() function returns a list. But In Python 3 version, the function returns a map
object which is a generator object. To get the result as a list, the built-in list() function
can be called on the map object. i.e. list(map(func, *iterables))
The number of arguments
to function must be the number of iterables listed.
Lets see how is this map
function rules with the codes…
my_games= [‘hockey’,’base ball’,’cricket’,’relayrace’]
uppered_games = []the above created var with list of games is been stored in variable
my_games..
for games in my_games:
games_ = games.upper()
uppered_games.append(games_)output:- ['HOCKEY', 'BASE BALL', 'CRICKET', 'RELAYRACE']Exaplaination:- the above for loop condition created a list of games
and converted all the characters into
Capital letters using
simple for loop condition..
We can pass as many iterable
objects as we want after passing the function we want to use:
# lets
understand with more additional functions without using lambdas and using def
function
def starts_with_A(s):
return s[0] == "A"
fruit = ["Apple",
"Banana", "Pear", "Apricot", "Orange"]
map_object =
map(starts_with_A, fruit)
print(list(map_object))output: [True, False, False,
True, False]
Explanation:- the above code
we performed created the variable of name
fruits in which list of fruits
with different characters are stored with the def function and the condition
commanded to give the output with the list of items which are contained with
character A should give the output with conditional statements with either True
or False statements so the above output provided with the results.. we even can
perform the same thing using lambda functions too..
The filter()
Function
Just like
to map(), filter() takes a function object and an
iterable and creates a new list.
Filter() name it self suggest that it gives
the only elements which passed returns the value, and satisfies the certain
conditions.
Filter Function
My_List = list(range(50))print([i for i in lst],end=",")output:- [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49]
Explanation:- the filter function create the variable
name my_list in which commanded condition created to give the all possible
outputs range of 0-50 values
Now, suppose we want to take only the odd numbers from
this list, or more clearly, we want to filter all the odd numbers from this list.
We first need the condition of how we will identify whether the number
is odd or not.
Let’s create a function odd_func, which will return true or false based
on if the number is odd or not.
The function passed to filter function should return boolean:
def is_odd(num):
return num%2!=0
# To use it with a list for filter, we will pass it as an argument in the
filter function.
filter_lst = filter(is_odd,lst)
print(type(filter_lst))#output:-
We can convert this filter obj to list by simply passing it to list
function.
filter_lst = list(filter_lst)
The reduce()
Function:-
Since we understood, about map, filter & its functions let’s see
about reduce () function and its uses
So reduce function works quite differently than map () and filter ()
functions, it will give single value as an output, in-fact it doesn’t gives the
list based output..
These all different functools module can be found in python3, isn’t a
built-in function anymore
Below is the syntax of reduce function.
reduce(function, sequence[, initial])
reduce() functions work taking
two arguments as function and sequence and passed first two items in the sequence
nd then gives the output in the form of sequence …
Let's understand its coding part and its output
# Note :- The coding part is in applied in python 3
from functools import reduce
def
do_sum(x1, x2):
return x1 + x2
reduce(do_sum,
[1, 2, 3,4])output:-
10For more such
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emerging new technologies do visit us at InsideAIML.
Happy Learning…