What is filter() in python?
Through the filter method, we filter out specific elements of a list using a filter condition defined in a separate function. So we first create a user-defined function which will mention the criteria of filtering. Together this function and the supplied list will be taken as parameters to the filter function to give us the result.
Syntax
filter(filter_function, sequence)
Example
In the below example we create a function that will find the even numbers present in a list. Then it will discard them (return false). The remaining odd numbers will be added to the final list. We can modify this function to filter out numbers divisible by 3 or 5 or so.
Live Demo
num_list = [6,17, 32, 11, 21, 132]
def remove_even(x):
if x%2 ==0 :
return False
else:
return True
odd_nos = filter(remove_even, num_list)
for x in odd_nos:
print(x)
Output
Running the above code gives us the following result −
17
11
21
Example
We can use the same approach to filter out vowels from a given list of alphabets. Here
Live Demo
letters = ['t','u','t','o','r','i','a','l','s']
def get_vowels(c):
if c in ['a','e','i','o','o']:
return True
else:
return False
vowel_list = filter(get_vowels, letters)
for w in vowel_list:
print(w)
Output
Running the above code gives us the following result −
u
o
i
a
Published on 17-Oct-2019 12:47:38
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