Python - Filter Function
filter() function calls the specified function which returns boolen for each item of the specified iterable (list).
filter(function, iterable) --> filter object
filter() function also receives two arguments, a function and a sequence (e.g. a list).
Each item in the list is processed by the function which returns True or False. Only those items which return True are stored in a filter object.
This can then be conveniently converted into a sequence.
Look at the following function
isPrime() which returns True if the parameter is a prime number, otherwise it returns False.
This function is used inside filter() along with a range object producing numbers between 2 and 100. Only prime numbers are collected in the resulting list object.
def isPrime(x): for n in range(2,x): if x%n==0: return False else: return True fltrObj=filter(isPrime, range(10)) print ('Prime numbers between 1-10:', list(fltrObj))
Prime numbers between 1-10: [3, 5, 7, 9]
The lambda function can also be used as a filter. The following program returns a list of even numbers from a range.
fltrObj=filter(lambda x: x%2==0, range(10)) print(list(fltrObj))