unfold function in python

Question

I have started practicing functional programming in python recently.

Lets say I define a function that gets an array of digits and concatenates it:

In [1]: def fromDigits(digits):
   ...:     return reduce(lambda x,y: 10*x+y,digits,0)
   ...:

In [2]: fromDigits([1,2,3,4,5])
Out[2]: 12345

Now I want to implement the reverse function:

def toDigits(num):
   return unfold(lambda m,digits: (m/10,digits+[m % 10]) if m>0 else None,  num,  [])

But I couldn't find a definition of unfold in the python functools or anywhere in the standard library.

Answer 1

unfold is not a python function ... here is a recursive solution ...

def to_digits(x):
    if not x: return []
    return to_digits(x//10) + [x%10]

to_digits(12345)