trouble with the map function

Question

I'm pretty new to python, and am playing around with codes for prime numbers, I created a function that tests the goldbach conjecture on any positive integer given, and returns False, 0, 0 if the conjecture does not apply, and returns True, p1, p2 if the given number follows the goldbach conjecture, for example, goldbach(10), would return True, 3, 7 or goldbach(21) would return True, 2, 19.

I also created a function that creates a list of prime numbers in a given range, is it possible to map my goldbach(n) function to this created list, so that it returns a new list containing something like [(bool, p1, p2), ..., (bool, p1, p2)]? If so, how would I go about coding this? Is the map() function even what I should be using? I believe I'm missing something important here, because I always get an error saying: 'tuple' object is not callable.

This is what is most likely causing the problem:

def goldbachlist(x):
  primes=listofprimes(x)
  gold=list(map(goldbach(x), primes))
  return gold

The first argument of map must be a function. Try: gold=list(map(goldback, primes) — cao-nv
– cao-nv, Commented May 8, 2022 at 5:02

Java-Enthusiast · Accepted Answer · 2022-05-08 05:30:18Z

1

I took a crack at creating the program from your specifications. I am not sure that you've implemented the functions you haven't listed the same way that I have, but I have tested this on my machine and have verified that I get the results you desire. Note that the post by jwillis0720 uses a more elegant list filtration practice.

def listofprimes(x):
s = []
for i in range(2, x):
    print(i)
    stop = False
    for z in range(1, i):
        if i % z == 0 and z != 1 and z != i:
            stop = True

    if not stop:
        s.append(i)

return s

def goldbach(x):
  primes = listofprimes(x)
  for i in primes:
    for j in primes:
        if i + j == x:
            return (True, i, j)


return (False, 0, 0)

def goldbachlist(x):
 primes = listofprimes(x)
 print(primes)
 gold=list(map(lambda x: goldbach(x), primes))
 finalG = []
 for g in gold:
    if(g[0] == True):
        finalG.append(g)

return finalG;

print(goldbachlist(int(500)))

answered May 8, 2022 at 5:30

Java-Enthusiast

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1 Comment

Nicholas Boscolo Over a year ago

I implemented them in a different way, but with the same general ideia, I really liked your solution though, will definitely take a closer look in to lambda functions since they seem super useful. Thank you!

jwillis0720 · Accepted Answer · 2022-05-08 05:03:56Z

1

If I understand right, you need to map your primes ot your goldbach function

def goldbachlist(x):
  primes=listofprimes(x)
  gold=list(map(lambda x: goldbach(x), primes))# gold will have [(True,3,7)...
  return gold

However if you are trying remove non primes, you can filter out the false form gold

def goldbachlist(x):
  primes=listofprimes(x)
  gold=list(map(lambda x: goldbach(x), primes))
  filtered_gold = list(filter(lambda x: x[0],gold))
  return filtered_gold

answered May 8, 2022 at 5:03

jwillis0720

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1 Comment

Nicholas Boscolo Over a year ago

I am not yet familiar with lambda functions, but this makes a lot of sense, thank you!

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