Check If Key Exists And Get The Value At The Same Time In Python?

Sometimes we may need to verify the existence of a key in a dictionary and make something if the corresponding value exists. Usually, I proceed in this way: if key in my_dict:

Solution 1:

If the situations with missing values are really exceptional then the exception handling is appropriate:

try:
    value = my_dict[key]
    # Do somethingexcept KeyError:
    pass

If both missing and present keys are to be handled then your first option is useful.

ifkeyin my_dict:
    value = my_dict[key]
    # Do something

The use of get doesn't provide any advantage in this specific situation. In contrary, you have to find a non-conflicting value to identify the missing key condition.

Solution 2:

As mentioned several times, exception handling is the way to go. However, if you want to use get and None is a possible value, create a new object to act as the "not found" sentinel. (Since you've just created the object, it's impossible for it to be a valid entry in your dict. Well, not impossible, but you would really have to go out of your way to add it to the dict.)

sentinel = object()
value = my_dict.get(key, sentinel)
if value isnot sentinel:
    # Do something with value

Solution 3:

if (dict.get('key') isnotNone) and ('key'indict):
    var = dict['key']

Second portion of if-statement may not be totally necessary but I have used this format in my own code and it does the job.