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Questions and Answers
Dictionaries are ordered collections of key-value pairs.
Dictionaries are ordered collections of key-value pairs.
False
In a dictionary, keys can be of any data type, including lists and dictionaries.
In a dictionary, keys can be of any data type, including lists and dictionaries.
False
A dictionary can be created using the dict() function with key-value pairs as arguments.
A dictionary can be created using the dict() function with key-value pairs as arguments.
False
The values() method returns a dictionary with all the values in the dictionary.
The values() method returns a dictionary with all the values in the dictionary.
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The get() method returns the value for a given key, or raises a KeyError if the key is not present.
The get() method returns the value for a given key, or raises a KeyError if the key is not present.
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The update() method returns a new dictionary with the updated key-value pairs.
The update() method returns a new dictionary with the updated key-value pairs.
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Dictionaries are immutable data structures, meaning they cannot be modified after creation.
Dictionaries are immutable data structures, meaning they cannot be modified after creation.
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The items() method returns a list of tuples, where each tuple contains a key-value pair.
The items() method returns a list of tuples, where each tuple contains a key-value pair.
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The del statement is used to add a new key-value pair to a dictionary.
The del statement is used to add a new key-value pair to a dictionary.
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A dictionary can contain duplicate keys.
A dictionary can contain duplicate keys.
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Study Notes
What is a Dictionary?
- A dictionary is an unordered collection of key-value pairs, where keys are unique and values can be of any data type.
- It is a mutable data structure, meaning it can be modified after creation.
Key Features of Dictionaries
- Keys: Must be immutable (e.g., strings, integers, tuples) and unique.
- Values: Can be of any data type, including strings, integers, lists, and other dictionaries.
- Key-Value Pairs: Each key is associated with a specific value.
Creating a Dictionary
- Can be created using the
{}syntax, with key-value pairs separated by commas. - Example:
my_dict = {"name": "John", "age": 30}
Accessing and Modifying Dictionary Elements
-
Accessing: Use the key to access the corresponding value, e.g.,
my_dict["name"]. -
Modifying: Update a value by assigning a new value to an existing key, e.g.,
my_dict["age"] = 31. -
Adding: Add a new key-value pair, e.g.,
my_dict[" occupation"] = "Developer". -
Removing: Use the
delstatement to remove a key-value pair, e.g.,del my_dict["age"].
Dictionary Methods
-
keys(): Returns a list of all keys in the dictionary. -
values(): Returns a list of all values in the dictionary. -
items(): Returns a list of all key-value pairs in the dictionary. -
get(): Returns the value for a given key, or a default value if the key is not present. -
update(): Updates the dictionary with new key-value pairs.
Dictionary Operations
-
Membership Testing: Use the
inoperator to check if a key is present in the dictionary, e.g.,"name" in my_dict. - Dictionary Concatenation: Not supported, as dictionaries are unordered and cannot be concatenated.
Dictionary Use Cases
- Configuration Files: Dictionaries are often used to store configuration settings, e.g., user preferences.
- Data Storage: Dictionaries can be used to store and manipulate data, such as user information or game state.
- Caching: Dictionaries can be used as a cache to store frequently accessed data.
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Description
Understand the basics of Python dictionaries, including creation, accessing, and modifying elements, as well as dictionary methods and operations.
