How to use python dictionary flexibly

As we all know, the dictionary (dict) object is the most commonly used data structure in Python. Someone in the community once jokingly said: "Python attempts to load the entire world with a dictionary." The importance of dictionaries in Python is self-evident. Here are a few This is a list of efficient use of dictionaries. I hope Python developers can make reasonable use of them in daily application development to make the code more Pythonic.

1. Use the in keyword to check whether keyexists(recommended learning : Python Video Tutorial)

There is a development philosophy in the Zen of Python:

There should be one-- and preferably only one --obvious way to do it.

Try to find one, preferably the only obvious solution. In Python2, you can use the has_key method to determine whether a key exists in the dictionary. Another way is to use the in keyword. However, it is strongly recommended to use the latter, because in is processed faster. Another reason is that the has_key method was removed in Python3. If you want to be compatible with both py2 and py3 versions of the code, using in is the best choice.

if 'name' in d:
 pass

2. Use get to get the value in the dictionary

Regarding getting the value in the dictionary, a simple way is to use d[x] to access the element. However, in this case, a KeyError error will be reported when the key does not exist. Of course, you can first use the in operation to check whether the key is in the dictionary and then obtain it, but this method does not comply with what is said in the Zen of Python:

Simple is better than complex.Flat is better than nested.

Good code should be simple and easy to understand, and a flat code structure is more readable. We can use the get method instead of if... else

print(d.get("name", "default"))

3. Use setdefault to set the default value for the key that does not exist in the dictionary

The function of setdefault is :

If the key exists in the dictionary, then the corresponding value is returned directly, which is equivalent to the get method

If the key does not exist in the dictionary, the second parameter in setdefault will be used as The value of the key, and then returns the value.

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