lambda-assignment (E731)

Derived from the pycodestyle linter.

Fix is sometimes available.

What it does

Checks for lambda expressions which are assigned to a variable.

Why is this bad?

Per PEP 8, you should "Always use a def statement instead of an assignment statement that binds a lambda expression directly to an identifier."

Using a def statement leads to better tracebacks, and the assignment itself negates the primary benefit of using a lambda expression (i.e., that it can be embedded inside another expression).

Example

f = lambda x: 2 * x

Use instead:

def f(x):
    return 2 * x