To begin with: what the ***** is a generator? Well, in simple terms, it’s like a function that returns an infinite sequence of values. That might sound crazy at first, but bear with us we promise this will make sense soon enough.
Let’s start by creating a basic generator using Python’s built-in `yield` keyword:
# A generator is a function that returns an infinite sequence of values.
# It is created using the `yield` keyword in Python.
# Let's create a basic generator that yields numbers from 0 to 9.
def my_generator():
# `range(10)` creates a sequence of numbers from 0 to 9.
# `for` loop iterates through each number in the sequence.
for i in range(10):
# `yield` keyword returns the current value of `i` and pauses the function.
yield i
# Now, let's call the generator function and store the returned generator object in a variable.
my_gen = my_generator()
# We can use the `next()` function to retrieve the next value from the generator.
# Each time `next()` is called, the generator resumes from where it left off.
# In this case, it will return the next number in the sequence.
print(next(my_gen)) # Output: 0
print(next(my_gen)) # Output: 1
print(next(my_gen)) # Output: 2
# We can also use a `for` loop to iterate through the generator and print all the values.
for num in my_gen:
print(num) # Output: 3, 4, 5, 6, 7, 8, 9
# Since the generator is infinite, it will continue to yield values as long as it is called.
# This is useful for generating large sequences without taking up too much memory.
# However, we need to be careful not to accidentally create an infinite loop.
This code defines a function called `my_generator`, which uses a `for` loop to iterate over the numbers 0 through 9. The `yield` keyword is used inside the loop to return each value as it’s generated, rather than waiting until all values have been computed before returning them at once (like you would with a regular function).
So what can we do with this generator? Well, for starters, we can use it in a `for` loop just like any other iterable:
# Define a generator function called my_generator
def my_generator():
# Initialize a variable called num with value 1
num = 1
# Use a while loop to generate values until num is greater than 10
while num <= 10:
# Use the yield keyword to return the current value of num
yield num
# Increment num by 1
num += 1
# Use a for loop to iterate through the values generated by my_generator
for num in my_generator():
# Print the current value of num
print(num)
# Output:
# 1
# 2
# 3
# 4
# 5
# 6
# 7
# 8
# 9
# 10
This code will output the numbers 0 through 9 one at a time. The key difference here is that each value is being generated on-the-fly, rather than being computed and stored in memory all at once (which can be useful for large datasets or other resource-intensive operations).
But wait there’s more! Generators also have some pretty cool features when it comes to error handling. For example:
# This function is a generator that will continuously yield values based on user input
def my_generator():
try:
# This while loop will continue to run until the user enters a non-integer value
while True:
# The yield keyword will return the value to the caller and pause the function until the next iteration
yield 1 / int(input("Enter a number: "))
# This except block will handle any ValueError that may occur when converting the user input to an integer
except ValueError:
# This print statement will inform the user that their input was invalid
print("Invalid input")
This code defines another generator that prompts the user to enter a series of numbers, and then returns those values one at a time. If the user enters an invalid value (e.g., a string instead of a number), the `ValueError` exception is caught and handled inside the generator itself without having to modify any other code in your program!
Just remember to use them wisely (and maybe avoid wearing lab coats while coding).