Python walrus operator

I recently discovered the assignment expression, also known as the walrus operator, which was introduced in Python 3.8

Here is how it works in several examples:

Let’s consider the following data structure:

fresh_vegetables = {
 ‘tomatoes’: 10,
 ‘cucumbers’: 8,
 ‘onions’: 5
}

---

Lets make a salad out of these vegetables:

if (count := fresh_vegetables('tomatoes', 0)) >= 2:
  pieces = slice_tomatoes(count)
else:
  pieces = 0
try:
  salads = make_salad(pieces)
except OutOfTomatoes:
  out_of_stock()

---

This is much more readable than the example without the walrus operator:

def make_salad(count):
    ....
pieces = 0
count = fresh_vegetables('tomatoes', 0)
if count >= 2:
   pieces = slice_tomatoes(count)
.....

---

Using the walrus operator gives us better readability of our code and less code lines to write and maintain.

It works too with a do/while loop construct.

Instead of

def pick_vegetables():
   ....
while fresh_vegetables:
  for vegetable, count in fresh_vegetables.items():
     batch = make_salad(vegetable, count)
  fresh_vegetables = pick_vegetables()

---

We do the following with the walrus operator:

while fresh_vegetables := pick_vegetables():
  for vegetable, count in fresh_vegetables.items():
     batch = make_salad(vegetable, count)