# Breaking Down Python’s String Reversal

I’ve known for a while that reversing a string in Python is `"text"[::-1]`. However, it’s only now that I’ve truly understood how that works. Here’s what I learned today!

**Breaking Down the Syntax**

String slicing in Python uses the `[start:stop:step]` syntax. Here’s what each part does when reversing a string:

* **Start** (`:`): Specifies the starting index. It defaults to the beginning of the string.
    
* **Stop** (`:`): Specifies the stopping index. It defaults to the end of the string.
    
* **Step** (`-1`): Determines the step size. A negative step, such as `-1`, means take one step backwards.
    

Let’s take the string `a1b2c3` . To reverse it, we’d use:

```plaintext
>>> "a1b2c3"[::-1]
'3c2b1a'
```

The fun part is you can use the step size to extract just the numbers or just the letters from this string. Let’s explore:

**Extract every second element (letters only):**

```plaintext
>>> "a1b2c3"[::2] 
'abc'
```

**Extract every second element starting from index 1 (numbers only):**

```plaintext
>>> "a1b2c3"[1::2] 
'123'
```

We can use negative step sizes to extract specific parts of the string in reverse order.

**Reverse and grab every second character (numbers):**

```plaintext
>>> "a1b2c3"[::-2] 
'321'
```

**Reverse and grab every second character starting from the second-to-last position (letters):**

```plaintext
>>> "a1b2c3"[-2::-2] 
'cba'
```