In Python, what is a 'Generator' and how is it different from a normal function?

Understanding Generators in Python

In Python, a 'Generator' is a specific type of function that allows you to declare a function that behaves like an iterator, enabling you to iterate over it using a loop, just as you could with a list.

Key Features of Python Generators

• 'Generator' functions yield one value at a time. This makes them different from normal functions, which return a value and then discard local variables.
• Unlike regular functions that return values once, generators can be paused and can resume where they left off when called again. This enables them to produce a sequence of results over time, rather than computing them at once and sending them back like a list.

Practical Example of Python Generators

Consider the following example. In order to generate a sequence of numbers from 0 to N, you could use a simple for-loop:

def firstN(n):
    num, nums = 0, []
    while num < n:
        nums.append(num)
        num += 1
    return nums

print(firstN(10))

This function, however, creates an entire list in memory. If you wanted to generate a very large list of numbers, it could potentially consume significant amounts of memory and slow down your program.

Now, consider the equivalent generator:

def firstN(n):
    num = 0
    while num < n:
        yield num
        num += 1

for i in firstN(10):
    print(i)

The generator function looks like a normal function, except for the use of the 'yield' keyword. Yet, it doesn't compute all values at once - it only generates them on-the-fly one at a time.

Best Practices and Additional Insights

• While creating generators, you should use 'yield' instead of 'return' for producing values.
• Generators are best for calculating large sets of results where you don’t want to allocate the memory for all results at the same time.
• When generators are executed, they don't return a value and then exit like normal Python functions, instead, they automatically suspend and resume their execution state around the last point of value generation.

Python Generators thus offer a powerful tool in Python - particularly useful when working with large streams of data that require on-the-fly computation, where memory efficiency is a concern.