Return to Answer

def my_func(working_list=None): if working_list is None: working_list = [] # alternative: # working_list = [] if working_list is None else working_list working_list.append("a") print(working_list) 

The docs say you should use None as the default and explicitly test for it in the body of the function.

def my_func(working_list=None): if working_list is None: working_list = [] # alternative: # working_list = [] if working_list is None else working_list working_list.append("a") print(working_list) 

The docs say you should use None as the default and explicitly test for it in the body of the function.

Aside

x is None is the comparison recommended by PEP 8:

Comparisons to singletons like None should always be done with is or is not, never the equality operators.

Also, beware of writing if x when you really mean if x is not None [...]

See also What is the difference between "is None" and "== None"

def my_func(working_list=None): if working_list is None: working_list = [] working_list.append("a") print(working_list) 

The docs say you should use None as the default and explicitly test for it in the body of the function.

def my_func(working_list=None): if working_list is None: working_list = [] # alternative: # working_list = [] if working_list is None else working_list working_list.append("a") print(working_list) 

The docs say you should use None as the default and explicitly test for it in the body of the function.

def myFunc(working_list=None): if working_list is None: working_list = [] working_list.append("a") print working_list 

is how I do it.

def my_func(working_list=None): if working_list is None: working_list = []   working_list.append("a") print(working_list) 

The docs say you should use None as the default and explicitly test for it in the body of the function.