How to avoid write similar code multiple times in this situation?

March 24, 2022

I have a code like that,

i = 0
l1 = ['a','b','c']
while(i < len(l1)):
    if i + 2 < len(l1):
        if  l1[i + 2] == 'c':
            print("ok")
        else:
            print("None,Error!")
    else:
        print("None,Error!")
    i += 1

As you can see, in the else part, print("None,Error!") are used in two times. In practice, they are very long but totally same so I want to merge them to make them simple.However, I need to check if i+2 is out of list bound, so I cannot rewrite it to

if i+2 < len(l1) and l1[i + 2] == 'c':

Is there any idea can solve this problem?

>Solution :

As Phu Ngo mentions, we can take advantage of short circuiting to write

i = 0
l1 = ['a','b','c']
while(i < len(l1)):
    if i + 2 < len(l1) and l1[i + 2]=='c':
        print("ok")
    else:
        print("None,Error!")
    i+=1

If i+2<len(l1) is false, then the expression l1[i + 2]=='c' is never evaluated, which means that no error is raised.

Another solution that can be considered here is a try/except clause.

i = 0
l1 = ['a','b','c']
while(i < len(l1)):
    try:
        if l1[i+2]=='c':
            print("ok")
        else:
            raise ValueError
    except Exception:
        print("None,Error!")
    i+=1

Both result in the printouts