[Tutor] confusing enumerate behavior

[Emad Nawfal (عماد نوفل)]

Hi Tutors,
I'm a little, actually a lot confused by the behavior of the enumerate
function here. I have a text and I want to get each word within the context
of the three preceding and the three following words.  I tried this:
#BEGIN
my_input = "one two three four five six seven eight nine ten"
text = my_input.split()
for i,v in enumerate(text):
    line =  text[i-3], text[i-2], text[i-1], v, text[i+1], text[i+2],
text[i+3]
    print line
# END
The ouput was not as I expected. It did not start from the beginning
(actually I had expected it to throw and exception immediately)
('eight', 'nine', 'ten', 'one', 'two', 'three', 'four')
('nine', 'ten', 'one', 'two', 'three', 'four', 'five')
('ten', 'one', 'two', 'three', 'four', 'five', 'six')
('one', 'two', 'three', 'four', 'five', 'six', 'seven')
('two', 'three', 'four', 'five', 'six', 'seven', 'eight')
('three', 'four', 'five', 'six', 'seven', 'eight', 'nine')
('four', 'five', 'six', 'seven', 'eight', 'nine', 'ten')
Traceback (most recent call last):
  File "enumerate.py", line 13, in <module>
    line =  text[i-3], text[i-2], text[i-1], v, text[i+1], text[i+2],
text[i+3]
IndexError: list index out of range
emad at emad-laptop:~/Desktop$

I then though of adding dummy words to the beginning and the end and exclude
them later like this:
#BEGIN
my_input = "one two three four five six seven eight nine ten"

text2 = " nothing " *6 + my_input + " nothing "* 6

text2 = text2.split()
for i,v in enumerate(text2[6:-6]):
    line =  text2[i-3], text2[i-2], text2[i-1], v, text2[i+1], text2[i+2],
text2[i+3]
    print line
#END

The output this time was even more confusing:
emad at emad-laptop:~/Desktop$ python enumerate.py
('nothing', 'nothing', 'nothing', 'one', 'nothing', 'nothing', 'nothing')
('nothing', 'nothing', 'nothing', 'two', 'nothing', 'nothing', 'nothing')
('nothing', 'nothing', 'nothing', 'three', 'nothing', 'nothing', 'nothing')
('nothing', 'nothing', 'nothing', 'four', 'nothing', 'nothing', 'one')
('nothing', 'nothing', 'nothing', 'five', 'nothing', 'one', 'two')
('nothing', 'nothing', 'nothing', 'six', 'one', 'two', 'three')
('nothing', 'nothing', 'nothing', 'seven', 'two', 'three', 'four')
('nothing', 'nothing', 'one', 'eight', 'three', 'four', 'five')
('nothing', 'one', 'two', 'nine', 'four', 'five', 'six')
('one', 'two', 'three', 'ten', 'five', 'six', 'seven')

Can somebody please explain what is going on here? Have I done something
wrong? How can this be fixed?

Thanks in anticipation,
Emad
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