Python Comprehensions Behavior

comp_behavior.py

things = {
    "foo": "bar",
    "baz": "bing",
}

for k, v in things.items():
    pass

print("k leaked: " + k)

[(k2, v2) for k2, v2 in things.items()]

print("k2 leaked: " + k2)

{k3: v3 for k3, v3 in things.items()}

try:
    msg = "k3 didn't leak: " + k3
except NameError as e:
    print("k3 didn't leak: " + str(e))

def foo(*args):
    print("foo was called with " + str(args))

print("test call to foo")
foo(1, 2, 3, 4)

print("generators are lazy")
(foo(k4, v4) for k4, v4 in things.items())

print("unless you eval them")
list((foo(k4, v4) for k4, v4 in things.items()))

output.txt

$jython main.py
k leaked: baz
k2 leaked: baz
k3 didn't leak: name 'k3' is not defined
test call to foo
foo was called with (1, 2, 3, 4)
generators are lazy
unless you eval them
foo was called with ('foo', 'bar')
foo was called with ('baz', 'bing')