Weird closure behavior in python

Question

Here is a simple code I have been dealing with :

def get():
    return [lambda: i for i in [1, 2, 3]]

for f in get():
    print(f())

The output to this code is 3 but how does it work internally?

Answer 1

Closures don't refer to variables but rather to scopes. Since the last value of i in its scope is '3', all three closures return the same. To "lock" the current value of a variable, create a new scope just for it:

def get() : return [ (lambda x: lambda: x)(i) for i in [ 1, 2, 3 ] ]
for f in get() : print( f() )