Cannot convert string to int in Python

Question

What's wrong with this python snippet:

for zhszam in pontok.keys():
    s = 0
    for p in pontok[zhszam]:
        if p.isdigit():
            s += int(p)
            print s
    pontok[zhszam] = s
return pontok

where pontok is {1: ['10', ' 5', ' 3', ' 10', ' 7'], 2: ['10', ' 5', ' 3', ' 10']}. It gives the following wrong output somehow:

10
10
{1: 10, 2: 10}

While the values should be the sum of the numbers.

Thanks in advance!

indentation as a start... – Fredrik Pihl Jun 14 '13 at 21:25 — Fredrik Pihl, Jun 14 '13 at 21:25

score 5 · Accepted Answer · answered Jun 14 '13 at 21:27

5

Every string except the first '10' has a leading space, which isn't a digit. Thus it's not being processed at all.

Try:

for p in pontok[zhszam]:
    p = p.strip()
    # ...

answered Jun 14 '13 at 21:27

Mark Ransom

299,747
42
398
622

Ashwini Chaudhary · Answer 2 · 2013-06-14T21:37:13.303

You should not use str.isdigit, it can break very easily. Better use a try-except block with int().

>>> dic = {1: ['10', ' 5', ' 3', ' 10', ' 7'], 2: ['10', ' 5', ' 3', ' 10']}
for k,v in dic.iteritems():
    s = 0
    for x in v:
        try:
            s += int(x)     #raises Error if the item is not a valid number
        except:              
            pass            #leave the item as it is if an error was thrown
    dic[k] = s 
...     
>>> dic
{1: 35, 2: 28}

score 1 · Answer 3 · edited May 23 '17 at 12:29

1

I'd rather comment than leave this as an answer, but I haven't the rep yet. This question will help you with stripping those leading spaces: Python remove all whitespace in a string

edited May 23 '17 at 12:29

Community

1
1

answered Jun 14 '13 at 21:30

Rune

133
7

Cannot convert string to int in Python

3 Answers3