Parsing my string to int is causing ValueError in python

Question

For some reason int(str) is causing an error. I can't work out why. I'm wondering if someone can tell me why.

cx4_list_reduce = ['[#1]',(1,3,5),(7,6,9)]
list2= ['[#2]',(2,5,4), (1,3,5), (5,8,1), (7,2,6)]
n2 =3
for process_tuple in cx4_list_reduce:
      d_num = ""
      if process_tuple == list2[0]:
            d_num = process_tuple[2:3]
      n1 = int(d_num)
      if n1 <= n2:
           print('n1 =< n2')
           continue
      else:
            print('n1 => n2')

Error: invalid literal for int() with base 10: ''

Martijn Pieters · Accepted Answer · 2015-06-14 09:50:22Z

3

Look closely at the condition:

d_num = ""
if process_tuple == list2[0]:
    d_num = process_tuple[2:3]

So what should happen when the if test is False (when the value is not equal to list2[0]? d_num remains an empty string and you cannot convert that to an integer.

The error message tells you exactly that; invalid literal for int() with base 10: '' tells you an empty string cannot be converted.

Your first value in the cx4_list_reduce list is '[#1]', and that string is not equal to list2[0] ('[#1] is not equal to '[#2]'), so the above equality test fails.

answered Jun 14, 2015 at 9:50

Martijn Pieters

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1 Comment

matt2605 Over a year ago

Wow, I'm impressed. I spent a whole on it.

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