In Python, you can iterate over a dictionary using a for loop. When iterating over a dictionary, you can access both the keys and values of the dictionary using the items() method. Here is an example of how to iterate over a dictionary in Python:
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my_dict = {"key1": "value1", "key2": "value2", "key3": "value3"} for key, value in my_dict.items(): print(f"Key: {key}, Value: {value}") |
This will output:
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Key: key1, Value: value1 Key: key2, Value: value2 Key: key3, Value: value3 |
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What is the time complexity of iterating over a dictionary in Python?
The time complexity of iterating over a dictionary in Python is O(n), where n is the number of key-value pairs in the dictionary. This is because each key-value pair needs to be visited and processed during the iteration.
What is dictionary unpacking in Python?
Dictionary unpacking in Python refers to a technique that allows you to quickly and easily extract key-value pairs from a dictionary and assign them to variables. This can be done using the double asterisk (**).
For example, given a dictionary person with keys 'name' and 'age':
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person = {'name': 'Alice', 'age': 30}
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You can unpack the dictionary like this:
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name, age = person['name'], person['age']
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Alternatively, you can use dictionary unpacking like this:
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name, age = person['name'], person['age']
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Either way, the variables name and age will be assigned the values 'Alice' and 30 respectively. This technique is particularly useful when working with functions that accept keyword arguments as dictionaries.
What is the difference between a dict and defaultdict in Python?
A dict is a built-in data type in Python that represents a collection of key-value pairs. It is a general-purpose mapping type that is commonly used to store data in Python.
On the other hand, defaultdict is a subclass of the dict class in the collections module in Python. defaultdict is a dictionary that provides a default value for keys that do not exist in the dictionary. When creating a defaultdict, you provide a default value that will be returned when a key that does not exist in the dictionary is accessed.
In summary, the main difference between a dict and defaultdict is that defaultdict provides a default value for keys that do not exist, while a dict does not.
How to get the length of a dictionary in Python?
You can get the length of a dictionary in Python by using the len() function. Here's an example:
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my_dict = {1: 'apple', 2: 'banana', 3: 'cherry'} dict_length = len(my_dict) print(dict_length) |
This will output:
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3
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In this example, the len() function is used to get the length of the my_dict dictionary, which contains 3 key-value pairs.
What is the difference between a dictionary and a list in Python?
In Python, a dictionary is a collection of key-value pairs, where each key is unique and maps to a specific value. Dictionaries are unordered and mutable, which means that the key-value pairs can be changed or removed.
On the other hand, a list is a collection of elements that are ordered and indexed starting from 0. Lists can contain duplicate elements and can store different data types. Lists are also mutable, which means that elements can be added, removed, or modified.
In summary, the main differences between a dictionary and a list in Python are:
- Dictionaries store key-value pairs, while lists store ordered elements.
- Dictionaries are unordered, while lists are ordered.
- Dictionaries use keys to access their values, while lists use indexes.
- Dictionaries are mutable, while lists are mutable.
What is the output of iterating over an empty dictionary in Python?
If you try to iterate over an empty dictionary in Python, there will be no output as there are no key-value pairs to iterate over. The loop will not run at all and the program will move to the next line of code after the loop.
