foo.py

def foo(bar=[]):
    bar.append("baz")
    return bar

foo1.py

def foo(bar=None):
    if bar=None:
        bar=[]
    bar.append("baz"0
    return bar

class A(object):
    x=1

class B(A):
    pass

class C(A):
    pass

>>>print A.x,B.x,C.x
1 1 1
>>>B.x=2
>>>print A.x,B.x,C.x
1 2 1
>>>A.x=3
>>>print A.x,B.x,C.x
3 2 3

try:
    l=["a","b"]
except (ValueError,IndexError) as e:
    pass

def create_multipliers():
    return [lambda x:i*x for i in range(5)]

for multiplier in create_multipliers():
    print multiplier(2)

def  create_multipliers():
    return [lambda x,i=i:i*x for i in range(5)]
for multiplier in create_multipliers():
    print multiplier(2)

#python2 python3 friendly compatiable
import sys
def bar(i):
    if i==1:
        raise KeyError(1)
    if i==2:
        raise ValueError(2)

def good():
    exception = None
    try:
        bar(int(sys.argv[1]))
    except KeyError as e:
        exception =e
        print('Key error')
    except ValueError as e:
        exception = e
        print('value error')
    print(exception)

good()