does anybody knows why this function doesn´t work very well:

f=lambda n: reduce(lambda x,y:x**2+y**2, map(int,str(n)))

I want that this function add the square of the digits of a number

an example of what i want:

f(442)=4**2+4**2+2**2=36 and it's giving me f(442)=1028!!!:S

However fou numbers with 2 digits the function works!

First, the newer Python constructions pretty much eliminate the need for "map()".

Try this:

``squaredigits = lambda x: sum([int(i)*int(i) for i in x])``

Jeff

Jeff's suggestion is modern Python. Make sure that your number is iterated as string:

``````squaredigits = lambda x: sum([int(i)*int(i) for i in str(x)])

print squaredigits(442)  # -->  36``````

Note: filter(), map() and reduce() will go away with Python30

``````# add this to future code
try: filter and map and reduce
except:
def filter(f, s): return [x for x in s if f(s)]
def map(f, *s): return [f(*x) for x in zip(*s)]
def reduce(f, s, i=None):
r = i
for x in s:
r = f(r, x)
return r``````

Part of the reason is that list comprehensions are simply so much faster than using defined function call. Also reduce() isn't used much. Good news is that lambda will stay.

Thanks it works!:)

Hey Henri, thanks for the info on Python30.