13 Python Generators

Question 1

What does a generator function do?

Answer 1

Generator functions allow us to write a function that can send back a value and then later resume to pick up where it left off. This type of function is a generator in Python, allowing us to generate a sequence of values over time. The main difference in syntax will be the use of a yield statement.

Question 2

What is the main keyword used to create generators?

Answer 2

yield

Question 3

What type of protocol does a generator function support?

Answer 3

iteration protocol

The main difference is when a generator function is compiled they become an object that supports an iteration protocol. That means when they are called in your code they don’t actually return a value and then exit. Instead, generator functions will automatically suspend and resume their execution and state around the last point of value generation.

Question 4

What does a very simple generator function look like?

Answer 4

def gencubes(n):
    for num in range(n):
        yield num**3

for x in gencubes(10):
print(x)

0
1
8
27
64
125
216
343
512
729

Question 5

What would a generator that calculates fibonacci numbers look like?

Answer 5

def genfibon(n):
    """
    Generate a fibonnaci sequence up to n
    """
    a = 1
    b = 1
    for i in range(n):
        yield a
        a,b = b,a+b

for num in genfibon(10):
print(num)

1
1
2
3
5
8
13
21
34
55

Question 6

What does the next() function do?

Answer 6

The next() function allows us to access the next element in a sequence. Lets check it out:

def simple_gen():
    for x in range(3):
        yield x

# Assign simple_gen 
g = simple_gen()

print(next(g))
0

Question 7

What happens if a generator has nothing else to yield?

Answer 7

You will get an exception.

StopIteration Traceback (most recent call last)
in ()
—-> 1 print(next(g))

StopIteration:

Question 8

Are iterables and iterators the same thing?

Answer 8

No.

Strings are iterables.

But they are not iterators.

Question 9

What function will turn a string into an iterator?

Answer 9

iter()

s = ‘hello’
s_iter = iter(s)
next(s_iter)
‘h’