CODEWITHSUNDEEP
pythonpython-2.7
Zid
Zid

Reputation: 449

Checking for None, False, True

Is there a more Pythonic way to implement this logic:

res = func()

if res is not None:         # res is either True, False, something else
    if res is True:                 
        #do something       # res is True
    elif res is False:                   
        #do something else  # res is False
    else:
        #do something else2 # res is not in [True,False]
else:                       
    #failed                 # res is None

Upvotes: 2

Views: 242

Answers (3)

Moinuddin Quadri
Moinuddin Quadri

Reputation: 48077

You may create a function to map the values to corresponding functions. Something like:

# Function to map values
def do_something(res):
    return {
        None: func_1,  # Each `res` mapped to corresponding function
        True: func_2,
        False: func_3,
    }.get(res, func_4)


do_something(res)()
#                ^ call the function returned by `do_something()`

The equivalent of the above code can be written based on your logic mentioned in question as:

if res is not None:
    if res is True:                 
        func_2()     
    elif res is False:                   
        func_3()
    else:
        func_4()
else:                       
    func_1()

Upvotes: 1

lionlinekz
lionlinekz

Reputation: 83

if res is None: 
    #do something   
elif res:
    #do something else
elif not res:
    #do something else 2

Upvotes: 0

Martijn Pieters
Martijn Pieters

Reputation: 1121924

No, you already have it covered.

Generally, don't use is True or is False, if you must have tri-state boolean, use:

if res is None:
    # handle None case
elif res:
    # handle true case
else:
    # handle false case

e.g. put the burden on the developer to use the tri-state correctly.

If the function needs to communicate more states, you should not use a boolean; in that case switch to using an enum value.

Upvotes: 6

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