Converting string to int in python

Question

a="1234"
for i in range(0,4):
            for k in range(i,4):
                s=int(a[i:k])
                print s

Output:

Traceback (most recent call last):
  File "C:/Python27/Solutions/test.py", line 4, in <module>
    s=int(a[i:k])
ValueError: invalid literal for int() with base 10: ''

can anybody tell me why I am getting this error ? i just want to print: 1 12 123 1234 2 23 234 and so on...

Because e.g. `a[0:0]` is an empty string `''` and `int('')` makes no sense. What output were you expecting? — jonrsharpe, Jan 02 '15 at 17:55
possible duplicate of [Parse String to Float or Int](http://stackoverflow.com/questions/379906/parse-string-to-float-or-int) — CyanogenCX, Jan 02 '15 at 18:07

score 2 · Answer 1 · answered Jan 02 '15 at 18:05

>>> a= "1234"
>>> a[0:0]   # in slice if start and end is same you will get empty string
''
>>> int(a[0:0])
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''
>>>

i think you want this??

>>> for i in range(3):
...     for k in range(i,4):
...         print int(a[i:k+1])
... 
1
12
123
1234
2
23
234
3
34

score 0 · Accepted Answer · edited Jan 02 '15 at 18:18

You are receiving this error because the first iteration of your loop (i=0,k=0) takes a[0:0]='' (empty string). Characters and numerical strings can be converted to integers, but an empty string isn't a character or string. It's the absence of characters.

If you were to guard this case your loop would subsequently take substrings of a (example '123', i=0, k=3) and this could be converted to the integer 123. The rest of the cases should output the desired integers just fine.

Converting string to int in python

2 Answers2