what does yield even mean, it is like return except it isnt?

 

 ## 🪄  Yield: Python's Magic for Lazy Number Sequences ✨

Ever wished you could create a sequence of numbers in Python without storing them all at once?   That's where `yield` comes in! It's like a magic trick for generating numbers on demand, making your code super memory-efficient.  

**What is `yield`?**

Imagine you have a treasure chest full of gold coins (numbers) . But instead of lugging the entire chest around, you use `yield` to create a special door  . Each time someone asks for a coin, you reach inside and hand them one, on the fly!  This way, you only deal with one coin at a time, saving your program from memory overload. 

Here's a breakdown:

1. You define a function with `yield` instead of `return`.

2. Inside the function, you perform calculations to generate the next number in the sequence.

3. When you call the function, it doesn't return all the numbers at once. Instead, it "yields" the first number.

4. Every time you use the function in a loop or iteration, it yields the next number in the sequence, just like grabbing another coin from the chest. 

**Reinventing `range` with `yield`**

The built-in `range` function is awesome, but let's see how we can create a similar function using `yield`:

```python

def my_range(start, stop, step=1):

  current = start

  while current < stop:

    yield current

    current += step

```

Here's what happens:

1. We define `my_range` with three arguments: `start`, `stop`, and an optional `step` (defaulting to 1).

2. Inside the function, we have a variable `current` that keeps track of the current number.

3. We use a `while` loop to iterate as long as `current` is less than `stop`.

4. Inside the loop, we `yield current`, making it available to whoever called the function. 

5. We then increment `current` by `step` to get the next number in the sequence.

**Using `my_range`**

Now, we can use `my_range` just like `range`:

```python

for num in my_range(1, 10):

  print(num)

```

This will print the numbers 1 to 9 (because the loop stops before reaching 10).

**Benefits of `yield`**

- **Memory Efficiency:** `yield` avoids creating a large list in memory, making it ideal for large sequences.

- **Flexibility:** You can control the generation of numbers with custom logic within the `yield` function.

**So, next time you need a sequence of numbers, consider using `yield` to work your memory-saving magic!  **

 

Interactive example:

https://colab.research.google.com/drive/1d9Rs8YtwdFLRTLpAAZ5y8Px7XQja-z-T?usp=sharing