Indexing and slicing python basics

okay, let's dive deep into indexing and slicing in python. these are fundamental operations for accessing and manipulating sequences like strings, lists, and tuples.

**what are indexing and slicing?**

* **indexing:** refers to accessing a single element within a sequence by its position (index).
* **slicing:** refers to extracting a sub-sequence (a portion) from a sequence.

**understanding indexes**

python uses zero-based indexing. this means the first element of a sequence is at index 0, the second at index 1, and so on.

* **positive indexes:** start from the beginning of the sequence (0, 1, 2, ...).
* **negative indexes:** start from the end of the sequence (-1, -2, -3, ...). -1 refers to the last element, -2 to the second-to-last, and so on.

**data types that support indexing and slicing**

the most common data types that support indexing and slicing are:

* **strings:** immutable sequences of characters.
* **lists:** mutable sequences of any python objects.
* **tuples:** immutable sequences of any python objects.

**1. indexing**

**basic syntax:**

**examples:**

**important notes about indexing:**

* **indexerror:** if you try to access an index that is out of range (e.g., a positive index equal to or greater than the length of the sequence, or a negative index that's "too far" back), you'll get an `indexerror`.



* **strings are immutable:** you can *read* a character at a specific index in a string, but you cannot *change* it directly using indexing.



* lists are mutable and their values can be changed with indexing:



**2. slicing**

slicing allows you to extract a contiguous portion (sub-sequence) of a sequence.

**basic syntax:**

* `start`: the index of the first element to include in the slice (inclusive). if omitted, it defaults to 0 (the beginning).
* `stop`: the index of the element *before* which the slice ends (exclusive). if omitted, it defaults to the end of the sequence.
* `step`: th ...

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