2

How can I convert these two functions to use lambda notation?

def sum_digits(number):
    if number == 0:
        return 0
    else:
        return (number % 10) + sum_digits(number / 10)

def count_digit(number):
    if number == 0:
        return 0
    else:
        return 1 + count_digit(number/10)
Raymond Hettinger
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Belovedad
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    Possible duplicate of [Can a lambda function call itself recursively in Python?](http://stackoverflow.com/questions/481692/can-a-lambda-function-call-itself-recursively-in-python) – Chiheb Nexus Apr 09 '17 at 02:37

5 Answers5

6
sum_digits = lambda number: 0 if number == 0 else (number % 10) + sum_digits (number / 10)

count_digit = lambda number: 0 if number == 0 else 1 + count_digit(number/10)

Incidentally, this is a bad time to use lambdas, since you need the function names in order for them to call themselves. The point of lambdas is that they're anonymous.

Arya McCarthy
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  • i thought i was wrong if i did that but it's just someone asking for this alternative method since i converted those two functions into an HOF already – Belovedad Apr 09 '17 at 02:40
  • Do you mean that you want a non-recursive form of each function? – Arya McCarthy Apr 09 '17 at 02:42
  • No, I purposely wrote them recursively. I just wanted to know how i could replace the function itself by using a lambda notation instead. My HOF does this: digits(number,term). Now I can replace term with the lambda function. – Belovedad Apr 09 '17 at 02:47
  • A perk of Python is that you don't even need to write them as lambdas to do that. Pass in the function as an argument. If I'm understanding your intent, you can call `digits(number, sum_digits)` even when it's not a lambda. – Arya McCarthy Apr 09 '17 at 02:49
  • I know, but I have never been good with lambda because I don't see the use of it most of the time. It was specifically required as an comment in my overall program. – Belovedad Apr 09 '17 at 02:52
5

A string-oriented approach wouldn't require recursion:

sum_of_digits = lambda n: sum(int(d) for d in str(n))
count_digit = lambda n: len(str(n))
martineau
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4

Use a conditional expression for the body of the lambda:

>>> sum_digits = lambda n: 0 if n == 0 else (n % 10) + sum_digits(n // 10)
>>> count_digit = lambda n: 0 if n == 0 else 1 + count_digit(n // 10)

Also, if is preferred to use // for the division so that the code will still work in Python 3.

Raymond Hettinger
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0
sum_digits = lambda number: 0 if number == 0 else (number % 10) + sum_digits (number//10)
count_digit = lambda number: 0 if number == 0 else 1 + count_digit(number//10)
print(sum_digits(2546))
print(count_digit(2546))

Will work on python 3 too...

Banee Ishaque K
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print(list(map(lambda x: sum(int(i) for i in str(x)),list(map(int,input().split())))))

this might be useful for reading and using lamda function on the same line.

Yunnosch
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Tanmayi
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