Key exists in nullable dict in python3

Question

I have a python dictionary object that will get value by a user. Also the user may leave it as None.

I want to check if my dict has a specific key or not, I tried if key in dict but I got argument of type 'NoneType' is not iterable error when my dict is None.

I need one line statement that returns False either my dict is None or my dict does not have that key.
Here is my code: (form is the dictionary)

if 'key' not in form:
    # Do somethin

can you please show us your code? Also do not use names that Python already uses like `dict`. Name your dicts something else — Ma0, Mar 28 '18 at 09:55

mhawke · Accepted Answer · 2018-03-28T10:11:08.340

2

Not sure why you must have a one-liner, but this is one:

False if d is None or k not in d else d[k]

Or (thanks @Chris_Rands for the hint)

False if not d else d.get(k, False)

If you simply want to test if the dict contains the key:

k in d if d else False

edited Mar 28 '18 at 10:11

answered Mar 28 '18 at 09:59

mhawke

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`False if d is None or d.get(k, False)` – Chris_Rands Mar 28 '18 at 10:00
@Chris_Rands - the `or` should be an `else`? – sjw Mar 28 '18 at 10:02
@Chris_Rands: good suggestion, but `else` would be better than `or`. – mhawke Mar 28 '18 at 10:03

score 2 · Answer 2 · answered Mar 28 '18 at 10:01

You can use a ternary togetether with dict.get(key, default):

d = None
k = d.get("myKex", False) if d else False  # dicts that are None are "False"

d = {2 : "GotIt"}
k2 = d.get("2", False) if d else False     # get() allows a default if key not present
k3 = d.get(2, False) if d else False       # got it ...


print (k, k2, k3)

Output:

(False, False, 'GotIt')

Further reading:

score 1 · Answer 3 · answered Mar 28 '18 at 10:02

1

One liner for checking not None and key presence. I assume my_dict has the values from user

result = (my_dict is not None) and (key in my_dict)

answered Mar 28 '18 at 10:02

shanmuga

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score 1 · Answer 4 · answered Mar 28 '18 at 10:05

1

Try to add the one line statement as follows:

True if dict and key in dict else False;

So then, returns False either dict is None or dict does not have that key.

answered Mar 28 '18 at 10:05

Kenny Aires

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score 0 · Answer 5 · answered Mar 28 '18 at 09:55

0

if dict is not None:
  if key in dict.keys():
    return True
return False

answered Mar 28 '18 at 09:55

shahaf

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thanks for the replay. but i need one line statement. – Mehrdad Pedramfar Mar 28 '18 at 09:56
@mehrdad-pedramfar you never *need* a one liner in Python – Chris_Rands Mar 28 '18 at 09:58

score -1 · Answer 6 · answered Mar 28 '18 at 09:58

-1

Try this:

if dict.has_key('specific-key-name-here'):

answered Mar 28 '18 at 09:58

rahul mehra

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https://stackoverflow.com/questions/1323410/has-key-or-in?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa – Mehrdad Pedramfar Mar 28 '18 at 10:01

Key exists in nullable dict in python3

6 Answers6