# how to use "filter" builtin function in python?

• "filter" is a python's built-in function which can be found in module "__builtin__".
• It takes two arguments, first argument as a function and second argument as sequence of objects/elements.
• It passes all objects/elements to given function one after other.
• If function returns "True" then it appends the object/element to a list & returns the list after passing all elements.
• If sequence is a tuple or string, it returns the same type, else return a list.
• If function is None, return the items that are true.

### Q. Find out the all prime numbers below hundred ?

`num = 100primes = []for i in range(2, 100):   for j in range(2, i):      if i % j == 0:         break   else:      primes.append(i)print(primes)# Output: [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]`

#### 2. Using function "filter"

`def is_prime(num):   for j in range(2, num):      if num % j == 0:         return False   else:      return Trueprimes = filter(is_prime, range(1, 100))print(primes)# Output: [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]print(type(primes))# Output: list`

### Lets test filter by passing "None" as first argument

`a = (0, 1, 2, 3)l = filter(None, a)print(l)# Output: (1, 2, 3)print(type(l))# Output: tuple`
It converts element to boolean if it returns true then it will add element to list/tuple/string.

### Let's apply "filter" on strings.

#### Remove vowels from string in python.

`def remove_vowels(char):    return char.lower() not in ['a', 'e', 'i', 'o', 'u']s = filter(remove_vowels, "this is anjaneyulu batta")print(s)# Output: ths s njnyl btt`