Get key from value in dictionary in Python
This article describes how to get a key from a value in a dictionary [dict type object] in Python.
- Get key from value with list comprehension and items[]
- Sample codes to extract keys with various conditions
To get the value from the key, just specify the key as follows.
You can also use the get[] method to get the value from the key. If you use the get[] method, no error will occur even if you specify a key that does not exist. See the following article.
- Get dictionary value from key with get[] in Python
You can also use the keys[] method to get a list of all keys.
- Iterate keys and values of dict with for loop in Python
Get key from value with list comprehension and items[]
To get the key from the value in the dictionary, use list comprehension and items[] method.
For list comprehensions and for loops for dictionaries, see the following articles.
- List comprehensions in Python
- Iterate keys and values of dict with for loop in Python
The following is a sample code to get a list of keys that are paired with a specified value. If the key with the specified value does not exist, an empty list is returned.
If you want to get the key itself instead of the list, you can specify the first element of the list with [0].
Note that if a key with the specified value does not exist, it will be an empty list, so specifying [0] will raise IndexError.
If you repeat the same operation, it is useful to make it a function.
For dictionaries that do not have duplicate values, the following function is also possible.
If a key with the specified value exists, that key is returned, otherwise None is returned. If the values are duplicated, one of the keys is returned.
Sample codes to extract keys with various conditions
In the above example, keys whose value is equal to the specified value are extracted.
You can extract keys under various conditions by changing the conditional expression part of the list comprehension.
Related Categories
- Python
- Dictionary
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