I'd like to programmatically create a list of functions, each of which returns a dictionary with a specific key, and always the same value. That is:
l1 = [lambda _: {0: 42}, lambda _: {2: 42}, lambda _: {3: 42}]
I'm trying to achieve the same result programmatically. To try and avoid the usual problem with lazy evaluation, I thought I'd only need to create a generator for generating the functions on the fly:
gen = (lambda _: {f: 42} for f in range(3))
And then use a simple list comprehension to get the list:
l2 = [f for f in gen]
That's not sufficient. In fact, if you compare func_clousures with one another, they're all the same:
x[0].func_closure == x[1].func_closure == x[2].func_closure # this is True
What's the best way to get the result I'm looking for?
You are assigning the last value of f to all the lambdas:
gen = (lambda _,f=f: {f: 42} for f in range(3))
As @Jon Clements so kindly pointed out the term is lazy binding, which is described in Common_Gotchas_In_Python