Example: Confusing syntax of walrus operator `:=`

[ipid]

Hello.

I found that the syntax of :=, the walrus operator as a new feature in Python 3.8, is kind of confusing and newbies may make mistakes on it.

Consider the following example:

a, b = 233, 233

# Try assigning to `a`, `b` in `if` statement
if (a, b := 0, 0):
    print(a, b)

The result is:

233 0

You can see that a is never assigned, because of the syntax of := operator:

NAME := expr

where NAME is a valid identifier and expr is a valid expression. Thus unpack assignment is not supported. And code (a, b := 0, 0) is just the same as (a, 0, 0).

You must choose either unpack assignment with normal = or the walrus operator :=.