How to filter the even and positive numbers from a list using functions-CodePudding

Given the list of integers stored in the variable numbers, declare the variable result1 and initialize the values of the initial list containing only the even positive numbers, respecting the initial order.

numbers = [-85,34,-7,-6,57,-6,-65,-49,-51,79,90,-75,33,36,9,30,-61,-66,95 .15,-56.45,-21,-81,-83,-31.82,-92,21.95,-70.88,-25,100,-17,-52,-74,-24.85 ,-40,-35,82,-74,-89,73,-44,53,88,35,-77,-90, 54,-41,-23,58,-95,47,-65, -92,91,64,-69,-21,-58, -63,-51,95,45,95,50,4,-15,-98,27,-84,32,57,-50, -54,-14,-46,98,76,0,-85,-1,15,67,-5,92,-39,-68, -73,-85,0,-39,-72, -9,52,27,52,-41,69,52,-42, -78,-37.59,-77,-30,77,56,-13,-80,-14,-30.94 ,34, 81,-46,-77,50,-23,-20,-59,-4,59,94,34,50,46,87, -78,88,-47,66,92,- 42,0,-28,-31,-18,-32,34,66,-12, 81,17,-11,37,20,-82,9,41,28,-81,26,47, 70.98, -82,-15.46,-13.89,-33,19,94,-88,52,14,27,-4, 6,-60.44,-98.83,-13 ,-80,-58,-10,-33,-70.87, -50.51,-3,-36,-60.61,-40,41.91,-25.38,-60.67 ,-85.36,-83.43]

What I tried to do:

def filterList(p, xs):
    return [x for x in xs if p(x)]

def ePar(numbers):
    return numbers%2==0
    
def ePositive(numbers):
    return numbers>0
    
def result1():
    return filterList(eEven, ePositive)


print (result1[:7]) ## because i want the last seven even positive integers

I expected that with my function result1, it would filter just the even and positive integers, but instead, the error was the following:

***Run error***
Traceback (most recent call last):
  File "__tester__.python3", line 35, in <module>
    print(resultado1[:7])
TypeError: 'function' object is not subscriptable

CodePudding user response：

The problem with your code is that your filterList function takes a function and a list of ints as an argument (type annotations added below for clarity):

from typing import Callable

def filterList(p: Callable[[int], bool], xs: list[int]) -> list[int]:
    return [x for x in xs if p(x)]

but you're calling it with two functions:

    return filterList(eEven, ePositive)   # two Callable[[int], bool]s

You could write your filterList to take an arbitrary number of functions instead, like this:

def filterList(xs: list[int], *p: Callable[[int], bool]) -> list[int]:
    return [x for x in xs if all(f(x) for f in p)]

and then call it like this:

def filterPositiveAndEven(xs: list[int]) -> list[int]:
    return filterList(xs, ePar, ePositive)

numbers = [-85,34,-7,-6,57,-6,-65,-49,-51,79,90,-75,33,36,9,30,-61,-66,95.15,-56.45,-21,-81,-83,-31.82,-92,21.95,-70.88,-25,100,-17,-52,-74,-24.85 ,-40,-35,82,-74,-89,73,-44,53,88,35,-77,-90, 54,-41,-23,58,-95,47,-65, -92,91,64,-69,-21,-58, -63,-51,95,45,95,50,4,-15,-98,27,-84,32,57,-50, -54,-14,-46,98,76,0,-85,-1,15,67,-5,92,-39,-68, -73,-85,0,-39,-72, -9,52,27,52,-41,69,52,-42, -78,-37.59,-77,-30,77,56,-13,-80,-14,-30.94 ,34, 81,-46,-77,50,-23,-20,-59,-4,59,94,34,50,46,87, -78,88,-47,66,92,- 42,0,-28,-31,-18,-32,34,66,-12, 81,17,-11,37,20,-82,9,41,28,-81,26,47, 70.98, -82,-15.46,-13.89,-33,19,94,-88,52,14,27,-4, 6,-60.44,-98.83,-13 ,-80,-58,-10,-33,-70.87, -50.51,-3,-36,-60.61,-40,41.91,-25.38,-60.67 ,-85.36,-83.43]
print(filterPositiveAndEven(numbers))
# prints [34, 90, 36, 30, 100, 82, 88, 54, 58, 64, 50, 4, 32, 98, 76, 92, 52, 52, 52, 56, 34, 50, 94, 34, 50, 46, 88, 66, 92, 34, 66, 20, 28, 26, 94, 52, 14, 6]

CodePudding user response：

I have no idea what your resultado1 or result1 variable is. I assume it to be the patent res variable used by programmers.

def filter_even_and_positive(num):
    return (num % 2 == 0 and num > 0)
res = []
for n in numbers:
    if filter_even_and_positive(n): res.append(n)
print(res[:7])

With list comprehension you could shorten your code into:

res = [n for n in numbers if (n % 2 == 0 and n > 0)]
print(res[:7])

Output:

[34, 90, 36, 30, 100, 82, 88]