Python UDF got problems converting Strings to Integers

[Björn-Elmar Macek]

Hi together,

i got a UDF that  sums up histograms in form of tuples. The function i 
wrote looks like this:

@outputSchema("res_histo:tuple()")
def aggHisto(aHistogramSet):
                if aHistogramSet is None: return None;
                hist_len = len(aHistogramSet[0])
                result=[0]*hist_len

                for aHistogram in aHistogramSet:
                        for i in range(0,hist_len):
                                value = 
int(''.join(map(str,aHistogram[i])));
                                result[i] = result[i] + (value)
                return tuple(result)

So for the following input {(1,23,45),(0,0,0)} i SHOULD get the 
following output: (1,23,45)
But instead i get: (49,5051,52,5353)
I played around with this for some time and found out this program does 
the following:
The line "value = int(''.join(map(str,aHistogram[i])));" does not 
convert the "23" to 23, but it does the following:
It takes every single digit starting with the most siginificant one and 
adds 48 to it: 2+48=50 and 3+48=51 resulting in 5051

Why does this happen? Can anybody help me here?

Best regards,
Elmar