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What's an elegant way to test for list index existing?


Ben Finney wrote:

> Ben Finney <ben+python at benfinney.id.au> writes:
> 
>> You can use a comprehension, iterating over the full range of index you
>> want::
>>
>>     words = shlex.split(line)
>>     padding_length = 5
>>     words_padded = [
>>         (words[index] if index < len(words))
>>         for index in range(padding_length)]
> 
> That omits the important case you were concerned with: when `index <
> len(words)` is false. In other words, that example fails to actually pad
> the resulting list.

It would if it weren't a syntax error. 

No harm done ;)

> Try this instead::
> 
>     words = shlex.split(line)
>     padding_length = 5
>     padding_value = None
>     words_padded = [
>         (words[index] if index < len(words) else padding_value)
>         for index in range(padding_length)]
>