Python Dictionaries Quiz
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Questions and Answers

What method can be used to remove a specific key from a dictionary and return its value?

  • discard()
  • remove()
  • pop() (correct)
  • delete()

The clear() method removes all items from a dictionary but keeps the dictionary itself.

True (A)

What method returns a view object displaying all the keys in a dictionary?

keys()

To merge two dictionaries, the _______ method is used.

<p>update()</p> Signup and view all the answers

Match the following functions with their descriptions:

<p>keys() = Returns a view of all the keys in the dictionary values() = Returns a view of all the values in the dictionary items() = Returns a view of key-value pairs as tuples get() = Retrieves value corresponding to a given key</p> Signup and view all the answers

Which of the following correctly prints the length of a dictionary named my_dict?

<p>print(len(my_dict)) (A)</p> Signup and view all the answers

Dictionaries allow for duplicate keys.

<p>False (B)</p> Signup and view all the answers

What will be the result of the statement my_dict.popitem() if the dictionary is empty?

<p>It will raise a KeyError.</p> Signup and view all the answers

What is a key characteristic of a Python dictionary?

<p>Keys must be unique. (B)</p> Signup and view all the answers

A Python dictionary can have duplicate keys.

<p>False (B)</p> Signup and view all the answers

What method can be used to safely access the value of a key without raising an error if the key does not exist?

<p>get()</p> Signup and view all the answers

A dictionary in Python is enclosed in ________.

<p>curly braces</p> Signup and view all the answers

Match the following dictionary types with their descriptions:

<p>Empty Dictionary = my_dict = {} Dictionary with Integer Elements = my_dict = {1: 'apple', 2: 'banana'} Nested Dictionary = my_dict = {'person': {'name': 'John'}} Single Element Dictionary = my_dict = {1: 'apple'}</p> Signup and view all the answers

What will my_dict.get(4) return if my_dict = {1: 'apple', 2: 'banana', 3: 'cherry'}?

<p>None (B)</p> Signup and view all the answers

You can modify the value of an existing key in a Python dictionary.

<p>True (A)</p> Signup and view all the answers

How would you check if a key exists in a dictionary?

<p>'key in my_dict'</p> Signup and view all the answers

What is one key feature of dictionaries compared to lists?

<p>Dictionaries are mutable and can directly change values. (D)</p> Signup and view all the answers

Keys in a dictionary can be of any type, including mutable types.

<p>False (B)</p> Signup and view all the answers

What is the expected output of counting word occurrences in the sentence 'Hello world, hello again, world!'?

<p>{'hello': 2, 'world,': 2, 'again,': 1}</p> Signup and view all the answers

A dictionary can be used as a set of ________ to keep track of the frequency of elements.

<p>counters</p> Signup and view all the answers

Match the following dictionary operations with their descriptions:

<p>counting occurrences = Tracking frequency of elements using keys changing values = Updating existing entry without creating a new object using immutable types = Keys must not change after creation case-insensitive counting = Counting elements without considering letter casing</p> Signup and view all the answers

In the provided example, what will be the output of the dictionary 'count_dict' after processing the list ['apple', 'banana', 'apple', 'orange', 'banana', 'banana']?

<p>{'apple': 2, 'banana': 3, 'orange': 1} (D)</p> Signup and view all the answers

What will the output be if you run the given word counting code on a file containing 'hello world hello'?

<p>{'hello': 2, 'world': 1} (D)</p> Signup and view all the answers

Dictionaries can only be used with string keys.

<p>False (B)</p> Signup and view all the answers

Write a function that counts how many times each character appears in the string 'hello' and returns the result in a dictionary.

<p>{'h': 1, 'e': 1, 'l': 2, 'o': 1}</p> Signup and view all the answers

The provided code only counts uppercase letters in the text file.

<p>False (B)</p> Signup and view all the answers

What data structure is used to store word counts in the first problem?

<p>dictionary</p> Signup and view all the answers

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}.

<p>3</p> Signup and view all the answers

Match the file names to their respective tasks:

<p>textfile.txt = Count word frequencies letters.txt = Count letter frequencies input.txt = Count specific words sample.txt = Count word occurrences using loops</p> Signup and view all the answers

In the letter counting problem, which characters are to be ignored?

<p>Spaces and punctuation (C)</p> Signup and view all the answers

The output for counting specific words in 'input.txt' includes the word 'hello'.

<p>False (B)</p> Signup and view all the answers

How many times does the word 'python' appear in the 'input.txt' example provided?

<p>2</p> Signup and view all the answers

Which method is used to remove a key from a dictionary and return its value?

<p>pop() method (A)</p> Signup and view all the answers

The del statement can be used to remove an item from a dictionary without returning its value.

<p>True (A)</p> Signup and view all the answers

What will be the merged dictionary when merging dict1 = {'apple': 1, 'banana': 2} and dict2 = {'cherry': 3, 'date': 4}?

<p>{'apple': 1, 'banana': 2, 'cherry': 3, 'date': 4}</p> Signup and view all the answers

To count the frequency of each fruit, you can create a dictionary named __________.

<p>fruits</p> Signup and view all the answers

Match the dictionary operations with their descriptions:

<p>del = Removes a key from a dictionary pop() = Removes a key and returns its value update() = Merges another dictionary into the current one items() = Returns a view object displaying a list of dictionary's key-value tuple pairs</p> Signup and view all the answers

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}')

<p>banana: 3 (A)</p> Signup and view all the answers

Dictionaries can be used to count word frequency in a text.

<p>True (A)</p> Signup and view all the answers

What function in Python is used to extract words from a string using regular expressions?

<p>re.findall</p> Signup and view all the answers

In the code word_count[word] = 1, the word_count dictionary is being used to count the __ counts of words.

<p>frequency</p> Signup and view all the answers

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)

<p>{'apple': 5, 'banana': 3, 'orange': 1} (D)</p> Signup and view all the answers

The print(key) statement inside a loop over a dictionary will print the values of the dictionary.

<p>False (B)</p> Signup and view all the answers

Given the dictionary {'apple': 2, 'banana': 3, 'cherry': 5}, which key has the maximum value?

<p>cherry</p> Signup and view all the answers

Flashcards

What is a Python dictionary?

An unordered collection of key-value pairs in Python, allowing you to store data by associating each item with a unique key.

What is an empty dictionary?

A Python dictionary where no key-value pairs are present.

What is a dictionary with integer elements?

A dictionary where the keys are integers and the values can be any data type.

What is a dictionary with mixed data types?

A dictionary where the keys and values can be of different data types.

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What is a nested dictionary?

A dictionary containing another dictionary within it.

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What is a single element dictionary?

A dictionary with only one key-value pair.

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What is the dict() constructor?

A way to create dictionaries using the dict() function.

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How do you access dictionary elements using keys?

You can access a dictionary element by using its key inside square brackets []. The code my_dict['key'] retrieves the value associated with the key 'key'.

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Dictionaries as Counters

A dictionary can be used to keep track of the frequency of elements (i.e., counts). This is particularly useful when counting occurrences in a list, string, or file.

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Count Word Occurences

A function that takes a sentence as input and counts the frequency of each word, returning a dictionary with words as keys and counts as values.

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Count Character Occurences

A function that counts the occurrences of each character in a given string, and returns the result in a dictionary.

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Dictionaries and Files

Dictionaries are helpful for working with files, such as processing data, counting occurrences, or organizing data in key-value pairs.

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Count Word Occurences in a File

A program that reads a file, counts the occurrences of each word (case-insensitive), and stores the results in a dictionary.

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How do you delete an item in a dictionary?

The del keyword permanently removes an item from a dictionary using its key.

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What does pop() do in a dictionary?

The pop() method removes and returns the value associated with a specific key. If the key doesn't exist, it raises a KeyError.

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What does .clear() do to a dictionary?

The .clear() method removes all key-value pairs from a dictionary, making it empty.

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What does the keys() method do?

The keys() method gives you a view object containing all keys in a dictionary.

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What does the values() method do?

The values() method returns a view object containing all values within a dictionary.

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What does the items() method do?

The items() method gives you a view object presenting key-value pairs as tuples.

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What does the get() method do?

The get(key) method returns the value associated with the key. If the key doesn't exist, it returns None instead of raising a KeyError.

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What does the update() method do?

The update() method merges the contents of another dictionary or iterable (containing key-value pairs) into the existing dictionary.

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Iterating through Keys

Iterating through a dictionary's keys one by one.

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Iterating through Values

Iterating through each value of a dictionary, one by one.

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Iterating through Key-Value Pairs

Iterating through both the key and value of each dictionary entry.

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Looping with Conditional Logic

Using conditional logic (like 'if' statements) within a loop to process specific entries in a dictionary based on their values.

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Word Frequency Counter

A dictionary where you can associate each unique word with its count from a text.

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Updating Dictionary Value

Updating the value associated with a key in a dictionary.

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Adding a New Item

Adding a new key-value pair to an existing dictionary.

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Finding Maximum Value

Finding the key with the maximum value in a dictionary.

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What is looping through a dictionary?

Iterating through the pairs within a dictionary, executing code for each key-value pair.

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How do you count word frequencies in a file?

Counting the frequency of each word in a text file. The keys are the words, and the values are their counts.

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What is case-insensitive counting?

A technique used to process data in a text file by breaking it down into individual words, and converting them to lowercase for case-insensitive counting.

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How are word frequency counts stored?

Storing the results of counting word frequencies in a dictionary, with words as keys and their counts as values.

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How do you access dictionary elements?

Accessing and modifying individual elements of a dictionary using their associated keys.

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What is updating a dictionary element?

Consistently applying an operation to each element in a dictionary.

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Can a dictionary have multiple values for a key?

The ability of dictionaries to handle multiple values associated with the same key, creating a list of values for that key.

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Removing a key-value pair using del

The del statement removes a key-value pair from a dictionary using the key as the argument. For example, del my_dict['key'] removes the key-value pair associated with the key 'key' from the dictionary my_dict.

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Removing a key-value pair using pop()

The pop() method removes a specific key-value pair from a dictionary and returns the value associated with the key. It takes the key to be removed as an argument. For example, value = my_dict.pop('key') removes the key-value pair associated with 'key' and assigns its value to the variable 'value'.

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Merging Dictionaries

Merging two dictionaries combines their key-value pairs into a single dictionary. If a key exists in both dictionaries, the value from the second dictionary overrides the value from the first dictionary.

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List of Tuples to Dictionary

Converting a list of tuples into a dictionary creates a new dictionary where the first element of each tuple becomes the key, and the second element becomes the value.

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Finding Frequency in a Dictionary

To find the frequency of an element in a dictionary, you access the value associated with the key that corresponds to the element. For example, frequency = my_dict['apple'] retrieves the frequency of the element 'apple' in the dictionary 'my_dict'.

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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 the get() method avoids errors if the key doesn't exist. By default, it returns None.

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 del keyword 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 or None if 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 del to 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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Related Documents

UNIT3: Python Dictionaries PDF

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.

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