ValueError: Substring not found when using str.index

Question

I am a beginner in python and the following code I am trying

input_number = raw_input("Please input the number:")
print type(input_number)
if(input_number.index('0')):
    print "Not Accepted"
else:
    print "Accepted"

When I am giving the input for example '1234506' its showing "Not accepted" which is valid but when I am giving '123456' its throwing error "Substring not found". So how can I print the else part.

Answer 1

when you enter 123456 or 1234506, python considers it as a string.

Now, when you use string_object.index(substring), it looks for the occurrence of substring (in your case, the substring is '0') in the string_object. If '0' is present, the method returns the index at which the substring is present, otherwise, it throws an error.

you can use the following instead :

if '0' in input_number :
    print 'not accepted'
else :
    print 'accepted'

Answer 2

str.index errors out when there is no match. In this situation, you can either choose to handle the error, or use str.find instead which returns an integer value between -1 and len(input_number), or do a set membership test on the original string.

Option 1

Conversion to set lookup:

if '0' not in set(input_number):
    print "Accepted"
else:
    print "Not accepted"

---

Option 2

Using try...except to handle the ValueError.

try:
    input_number.index('0')
    print "Not accepted"

except ValueError:
    print "Accepted"

---

Option 3

Using str.find:

if input_number.find('0') < 0:
    print "Accepted"
else:
    print "Not accepted"