Issue
Is it possible in python to create an un-linked copy of a function? For example, if I have
a = lambda(x): x
b = lambda(x): a(x)+1
I want b(x)
to always return x+1
, regardless if a(x)
is modified not. Currently, if I do
a = lambda(x): x
b = lambda(x): a(x)+1
print a(1.),b(1.)
a = lambda(x): x*0
print a(1.),b(1.)
the output is
1. 2.
0. 1.
Instead of being
1. 2.
0. 2.
as I would like to. Any idea on how to implement this? It seems that using deepcopy
does not help for functions. Also keep in mind that a(x)
is created externally and I can't change its definition. I've also looked into using this method, but it did not help.
Solution
You could define b like this:
b = lambda x, a=a: a(x)+1
This makes a
a parameter of b
, and therefore a local variable. You default it to the value of a
in the current environment, so b
will hold onto that value. You don't need to copy a
, just keep its current value, so that if a new value is created, you have the one you wanted.
That said, this sounds like something unusual happening, and if you tell us more about what's going on, there's likely a better answer.
Answered By - Ned Batchelder Answer Checked By - Katrina (PHPFixing Volunteer)
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