How Python String array work?

Question

i have a python string
word = helloworld
the answer for
word[1:9:2] will be given as "elwr". How this is happening? Thank you!!

Answer 1

You're asking for an explanation of Python's slice notation. See this answer for details. In particular, notice that:

word = 'helloworld'
word[1:9:2]

... Is stating that a new slice should be created, beginning at index 1, up to (and not including) index 9, taking one element every two indexes in the string. In other words, create a new string with the following elements:

0 1 2 3 4 5 6 7 8 9
h e l l o w o r l d
  ^   ^   ^   ^  

... And that's how you obtain 'elwr' as a result.

Answer 2

This means that you are taking a sub-string from position[1] to position[9] and in that you are taking only the 2nd letter. Sub-string would be something like :

elloworld

and since you are taking the character at index 2 from that it would be :

elwr

Also its not an array. Its just a string.

Answer 3

array[begin:end:step]

word[1:9:2] means you begin at index 1, and up until index 9, take every second letter.

Answer 4

That is array slicing - word[start_pos:end_pos:step], where start_pos and end_pos are zero-indexed and step is the value at which the index is incremented on each iteration. The character/element at end_pos is omitted from the result.

|h|e|l|l|o|w|o|r|l|d|
0 1 2 3 4 5 6 7 8 9 10
  ^---------------^
  start           end

Since step = 2 in your example, we would just take every other character from the range above.

>>> word = "helloworld"
>>> word[1]
'e'
>>> word[1:9]
'elloworl'
>>> word[1:9:2]
'elwr'