The sole advantage that a lambda expression has over a def is that the lambda can be anonymously embedded within a larger expression. If you are going to assign a name to a lambda, you are better off just defining it as a def.
From the PEP 8 Style Guide:
def f(x): return 2*x
f = lambda x: 2*x
The first form means that the name of the resulting function object is specifically ‘f’ instead of the generic ‘<lambda>’.
This is more useful for tracebacks and string representations in general.
The use of the assignment statement eliminates the sole benefit a lambda expression can offer over an explicit def statement (i.e. that it can be embedded inside a larger expression)
The following code assigns a lambda function which returns the double of its input to a variable. This is functionally identical to creating a def.
f = lambda x: 2 * x
Refactor the lambda expression into a named def expression.
def f(x): return 2 * x