Python Recursion: Range

Question

I need to define a function called rec_range(n) which takes a natural number and returns a TUPLE of numbers up to the number n.

i.e. rec_range(5) returns (0,1,2,3,4)

Answer 1

This is nice and concise, I think:

def rec_range(n):
    if not n <= 1: return rec_range(n-1) + (n-1,)
    return (0,)

Basically you recurse downwards until you reach 1, and for each recursion add one less than the number that you just recursed on position wise to your tuple.

Outputs:

>>>rec_range(4)
(0, 1, 2, 3)

Answer 2

this is simple one:

def getrange(a,b,c=1): 
     if a < b: 
        print(a)
        a+=c  
        getrange(a,b,c)
    else:
        return

getrange(0,30,2)

Answer 3

How about a one-liner:

def rec_range(n):
    return rec_range(n-1) + (n-1,) if n > 0 else ()

Or with lambdas:

rec_range = lambda n: rec_range(n-1) + (n-1,) if n > 0 else ()

Answer 4

I would write it as follows:

def rec_range(n):
    if n < 1:
        return ()
    else:
        return rec_range(n - 1) + (n - 1,)

print(rec_range(4)) # prints (0, 1, 2, 3)

This can also handle negative arguments.

Answer 5

Just keep concatenating tuples for the number that is one less until one is reached:

rec_range = lambda n: rec_range(n - 1) + (n - 1,) if n > 0 else ()