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There are several different ways to check if a Python dictionary contains a specific key, i.e.
d = {}
if key in d:
if d.contains(key):
if d.has_key(key):
it's silly for a language to allow you to do the same thing several different ways, UNLESS, each of the methods was doing something entirely different. Could someone please contrast the three techniques above, how are they different?
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Using has_key() method returns true if a given key is available in the dictionary, otherwise, it returns a false. With the Inbuilt method has_key(), use the if statement to check if the key is present in the dictionary or not.
To simply check if a key exists in a Python dictionary you can use the in operator to search through the dictionary keys like this: pets = {'cats': 1, 'dogs': 2, 'fish': 3} if 'dogs' in pets: print('Dogs found!') # Dogs found! A dictionary can be a convenient data structure for counting the occurrence of items.
Method 2: Extract specific keys from the dictionary using dict() The dict() function can be used to perform this task by converting the logic performed using list comprehension into a dictionary.
You can use the get() method of the dictionary ( dict ) to get any default value without an error if the key does not exist. Specify the key as the first argument. The corresponding value is returned if the key exists, and None is returned if the key does not exist.
They're all the same and they're all around for historical reasons, but you should use key in d.
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