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Questions and Answers
What method can be used to remove a specific key from a dictionary and return its value?
What method can be used to remove a specific key from a dictionary and return its value?
The clear() method removes all items from a dictionary but keeps the dictionary itself.
The clear() method removes all items from a dictionary but keeps the dictionary itself.
True
What method returns a view object displaying all the keys in a dictionary?
What method returns a view object displaying all the keys in a dictionary?
keys()
To merge two dictionaries, the _______ method is used.
To merge two dictionaries, the _______ method is used.
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Match the following functions with their descriptions:
Match the following functions with their descriptions:
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Which of the following correctly prints the length of a dictionary named my_dict?
Which of the following correctly prints the length of a dictionary named my_dict?
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Dictionaries allow for duplicate keys.
Dictionaries allow for duplicate keys.
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What will be the result of the statement my_dict.popitem() if the dictionary is empty?
What will be the result of the statement my_dict.popitem() if the dictionary is empty?
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What is a key characteristic of a Python dictionary?
What is a key characteristic of a Python dictionary?
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A Python dictionary can have duplicate keys.
A Python dictionary can have duplicate keys.
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What method can be used to safely access the value of a key without raising an error if the key does not exist?
What method can be used to safely access the value of a key without raising an error if the key does not exist?
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A dictionary in Python is enclosed in ________.
A dictionary in Python is enclosed in ________.
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Match the following dictionary types with their descriptions:
Match the following dictionary types with their descriptions:
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What will my_dict.get(4) return if my_dict = {1: 'apple', 2: 'banana', 3: 'cherry'}?
What will my_dict.get(4) return if my_dict = {1: 'apple', 2: 'banana', 3: 'cherry'}?
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You can modify the value of an existing key in a Python dictionary.
You can modify the value of an existing key in a Python dictionary.
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How would you check if a key exists in a dictionary?
How would you check if a key exists in a dictionary?
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What is one key feature of dictionaries compared to lists?
What is one key feature of dictionaries compared to lists?
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Keys in a dictionary can be of any type, including mutable types.
Keys in a dictionary can be of any type, including mutable types.
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What is the expected output of counting word occurrences in the sentence 'Hello world, hello again, world!'?
What is the expected output of counting word occurrences in the sentence 'Hello world, hello again, world!'?
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A dictionary can be used as a set of ________ to keep track of the frequency of elements.
A dictionary can be used as a set of ________ to keep track of the frequency of elements.
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Match the following dictionary operations with their descriptions:
Match the following dictionary operations with their descriptions:
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In the provided example, what will be the output of the dictionary 'count_dict' after processing the list ['apple', 'banana', 'apple', 'orange', 'banana', 'banana']?
In the provided example, what will be the output of the dictionary 'count_dict' after processing the list ['apple', 'banana', 'apple', 'orange', 'banana', 'banana']?
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What will the output be if you run the given word counting code on a file containing 'hello world hello'?
What will the output be if you run the given word counting code on a file containing 'hello world hello'?
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Dictionaries can only be used with string keys.
Dictionaries can only be used with string keys.
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Write a function that counts how many times each character appears in the string 'hello' and returns the result in a dictionary.
Write a function that counts how many times each character appears in the string 'hello' and returns the result in a dictionary.
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The provided code only counts uppercase letters in the text file.
The provided code only counts uppercase letters in the text file.
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What data structure is used to store word counts in the first problem?
What data structure is used to store word counts in the first problem?
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The expected output for counting letters is {'h': 1, 'e': 1, 'l': __, 'o': 2, 'w': 1, 'r': 1, 'd': 1, 'p': 1, 'y': 1, 't': 1, 'n': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1}.
The expected output for counting letters is {'h': 1, 'e': 1, 'l': __, 'o': 2, 'w': 1, 'r': 1, 'd': 1, 'p': 1, 'y': 1, 't': 1, 'n': 1, 'i': 1, 's': 1, 'f': 1, 'u': 1}.
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Match the file names to their respective tasks:
Match the file names to their respective tasks:
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In the letter counting problem, which characters are to be ignored?
In the letter counting problem, which characters are to be ignored?
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The output for counting specific words in 'input.txt' includes the word 'hello'.
The output for counting specific words in 'input.txt' includes the word 'hello'.
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How many times does the word 'python' appear in the 'input.txt' example provided?
How many times does the word 'python' appear in the 'input.txt' example provided?
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Which method is used to remove a key from a dictionary and return its value?
Which method is used to remove a key from a dictionary and return its value?
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The del statement can be used to remove an item from a dictionary without returning its value.
The del statement can be used to remove an item from a dictionary without returning its value.
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What will be the merged dictionary when merging dict1 = {'apple': 1, 'banana': 2} and dict2 = {'cherry': 3, 'date': 4}?
What will be the merged dictionary when merging dict1 = {'apple': 1, 'banana': 2} and dict2 = {'cherry': 3, 'date': 4}?
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To count the frequency of each fruit, you can create a dictionary named __________.
To count the frequency of each fruit, you can create a dictionary named __________.
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Match the dictionary operations with their descriptions:
Match the dictionary operations with their descriptions:
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What will the output of the following code be?
my_dict = {'apple': 2, 'banana': 3, 'cherry': 1} for key, value in my_dict.items(): if value > 2: print(f'{key}: {value}')
What will the output of the following code be?
my_dict = {'apple': 2, 'banana': 3, 'cherry': 1} for key, value in my_dict.items(): if value > 2: print(f'{key}: {value}')
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Dictionaries can be used to count word frequency in a text.
Dictionaries can be used to count word frequency in a text.
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What function in Python is used to extract words from a string using regular expressions?
What function in Python is used to extract words from a string using regular expressions?
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In the code word_count[word] = 1, the word_count dictionary is being used to count the __ counts of words.
In the code word_count[word] = 1, the word_count dictionary is being used to count the __ counts of words.
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What will be the output of the following code after executing?
my_dict = {'apple': 2, 'banana': 3} my_dict['apple'] = 5 my_dict['orange'] = 1 print(my_dict)
What will be the output of the following code after executing?
my_dict = {'apple': 2, 'banana': 3} my_dict['apple'] = 5 my_dict['orange'] = 1 print(my_dict)
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The print(key) statement inside a loop over a dictionary will print the values of the dictionary.
The print(key) statement inside a loop over a dictionary will print the values of the dictionary.
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Given the dictionary {'apple': 2, 'banana': 3, 'cherry': 5}, which key has the maximum value?
Given the dictionary {'apple': 2, 'banana': 3, 'cherry': 5}, which key has the maximum value?
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Study Notes
Python Dictionaries
- A dictionary in Python is an unordered collection of key-value pairs.
- Keys must be unique and immutable (e.g., strings, numbers, tuples).
- Values can be of any data type.
- Dictionaries are mutable, meaning their contents can be changed after creation.
- Dictionaries are enclosed in curly braces
{}, with key-value pairs separated by a colon:.
Types of Dictionaries
-
Empty Dictionary: An empty dictionary is created with empty curly braces
{}. - Dictionary with Integer Elements: Dictionaries can have integer keys, paired with other data type values.
- Dictionary with Mixed Data Types: Dictionaries can store various data types as keys and values.
- Nested Dictionary: A dictionary can contain another dictionary.
- Single Element Dictionary: A dictionary with only one key-value pair.
Accessing Dictionary Elements
-
Using Keys: Elements are accessed by using their corresponding keys inside square brackets
[]. -
Using
get()Method: Retrieving a value using theget()method avoids errors if the key doesn't exist. By default, it returnsNone.
Modifying Dictionaries
- Adding Items: New key-value pairs can be added by assigning a value to a new key.
- Changing Values: The value associated with an existing key can be modified by assigning a new value to that key.
Removing Items
-
Using
del: Removes an item by specifying its key. -
Using
pop(): Removes and returns a value associated with a key. -
Clearing the Dictionary: Removes all items from a dictionary using the
clear()method. -
Deleting the Entire Dictionary: The
delkeyword can be used to delete the entire dictionary.
Dictionary Methods
-
keys(): Returns a view object containing all the keys. -
values(): Returns a view object containing all the values. -
items(): Returns a view object containing all the key-value pairs as tuples. -
get(): Returns the value associated with a given key orNoneif the key doesn't exist. -
popitem(): Removes and returns an arbitrary key-value pair from the dictionary. -
update(): Updates a dictionary with elements from another dictionary or an iterable of key-value pairs.
Iterating Through Dictionaries
- Iterating through keys: You can iterate through the keys of a dictionary.
- Iterating through values: You can iterate through the values of a dictionary.
- Iterating through key-value pairs: You can iterate through both keys and values simultaneously.
Dictionaries and Files
- Dictionaries facilitate tasks like processing data from files, counting word occurrences, and organizing data in key-value formats from text files.
- Example problems involve processing words or characters from text files and storing results in dictionaries for further analysis or manipulation.
Word Frequency Counter
- Programs can count the occurrences of each word in text, ignoring case and punctuation.
- Data structures like dictionaries are used to store word frequencies.
Adding/Updating Key-Value Pairs
- Example of creating a dictionary with initial key-value pairs.
- Example of updating a value associated with an existing key.
- Example of adding a new key-value pair to a dictionary.
Finding Maximum Value in a Dictionary
- Programs can identify the key corresponding to the maximum value.
Iterating Through a Dictionary
- Iterating through the keys, values, and key-value pairs of a dictionary separately and collectively.
Removing Items from a Dictionary
- Using
delto remove items by keys. - Using
pop()to remove and return the value of an item. - Modifying the dictionary after removing items.
Simple Text Parsing: Capitalized Words
- Programs extract and count capitalized words in a text string.
- The extracted words are stored in a dictionary to count and display their frequency.
Merging Two Dictionaries
- Combining two dictionaries into a single dictionary.
Converting List of Tuples to a Dictionary
- Converting a list of tuples into a dictionary.
Frequency of Elements in a Dictionary
- Finding the count of a specific element within a dictionary.
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Description
Test your knowledge on Python dictionaries with this quiz. Questions cover methods for manipulating dictionaries, their characteristics, and behavior when accessing values. Ideal for learners looking to strengthen their understanding of Python data structures.
