How does FILTER and MAP works in Python

Question

How are those function/methods used,when to use them

Answer 1

filter & map is applied on lists , sets etc .
filter is used to take out some certain elements which satisy a particular condition ,& map is used to apply transformation function on every element .
//in very simple words , general meaning .

Answer 2

You use them when you want to apply a function over and over on different values and store them (map) or to apply a test on a list of values and only keep the values that get through the test (filter).

Let me add an example. My function figures out if a number is a 'Howling Prime' (whatever that is).

So if I call it once, I will get one result: True or False.

By applying the function on a range of values, I can keep only these that check as True and them.

https://code.sololearn.com/ckSkf5AE9B8T/?ref=app

The * just means: Open the box with the results and take them out (in this case in order to print them one by one).

Answer 3

map functions expects a function object and any number of iterables like list, dictionary, etc. It executes the function_object for each element in the sequence and returns a list of the elements modified by the function object
Here is an code which van help u understand better

def multi(x):
return x * 2
map(multi, [1, 2, 3, 4])

It can also reduce with the help of using lambda like this
map(lambda x : x*2, [1, 2, 3, 4])

filter function expects two arguments, function_object and an iterable. function_object returns a boolean value. function_object is called for each element of the iterable and filter returns only those element for which the function_object returns true.

For better understanding i want to give an simple example which help you
a = [1, 2, 3, 4, 5, 6]
filter(lambda x : x % 2 == 0, a)
Because only element in list whose mod 2 is equal to 0 will print
# Output: [2, 4, 6]