Practical Examples and Use Cases
Now that you've learned the basics of assignment expressions and how to apply them in loops, let's explore some practical examples and use cases.
Assignment expressions can be particularly useful when you need to filter and transform data within a loop. For example, let's say you have a list of numbers and you want to create a new list containing only the even numbers, with each number doubled.
## Traditional approach
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers = []
for num in numbers:
if num % 2 == 0:
even_numbers.append(num * 2)
print(even_numbers) ## Output: [4, 8, 12, 16, 20]
## Using assignment expressions
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers = [num * 2 for num in numbers if (doubled_num := num * 2) % 2 == 0]
print(even_numbers) ## Output: [4, 8, 12, 16, 20]
In the second example, the assignment expression (doubled_num := num * 2)
calculates the doubled value of each number and assigns it to the doubled_num
variable, which is then used in the list comprehension condition to filter for even numbers.
Accumulating Values
Assignment expressions can also be useful when you need to accumulate values within a loop. For example, let's say you have a list of numbers and you want to calculate the running sum.
## Traditional approach
numbers = [1, 2, 3, 4, 5]
running_sum = 0
for num in numbers:
running_sum += num
print(running_sum) ## Output: 15
## Using assignment expressions
numbers = [1, 2, 3, 4, 5]
running_sum = 0
for num in numbers:
running_sum := running_sum + num
print(running_sum) ## Output: 15
In the second example, the assignment expression running_sum := running_sum + num
updates the running_sum
variable within the loop, allowing you to accumulate the values in a more concise way.
Handling Errors and Edge Cases
Assignment expressions can also be useful when you need to handle errors or edge cases within a loop. For example, let's say you have a list of strings and you want to convert them to integers, skipping any values that cannot be converted.
## Traditional approach
data = ["1", "2", "3", "four", "5"]
valid_numbers = []
for item in data:
try:
num = int(item)
valid_numbers.append(num)
except ValueError:
continue
print(valid_numbers) ## Output: [1, 2, 3, 5]
## Using assignment expressions
data = ["1", "2", "3", "four", "5"]
valid_numbers = [int(item) for item in data if (num := int(item, None)) is not None]
print(valid_numbers) ## Output: [1, 2, 3, 5]
In the second example, the assignment expression (num := int(item, None))
attempts to convert each item to an integer, and the resulting value is assigned to the num
variable. The if
condition then checks if num
is not None
, which indicates a successful conversion, and includes the item in the list comprehension.
By exploring these practical examples, you can start to see how assignment expressions can be leveraged to write more concise and efficient Python code, especially when working with loops and data manipulation tasks.