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Questions and Answers
What is the primary difference between lists and arrays in Python?
Which data type can be stored in an array?
What must be included in your code when working with arrays in Python?
Why are tuples preferred over lists for certain applications?
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What type of data structure is ideal for creating a relationship between keys and values?
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What are the components of a dictionary in Python?
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Which method would you use to remove a specific item from a dictionary?
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When updating a value for a key in a dictionary, what happens if the key does not exist?
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What will happen if you use the clear() function on a dictionary?
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Which of the following is true regarding the keys in a dictionary?
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What is the output of the dictionary after the operation del(D['Name'])?
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What will be the result of executing D.pop('Age')?
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What does the output D.clear() produce?
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Which of the following statements about Python arrays is incorrect?
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What is the initial length of an empty dictionary created as 'M'?
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Which operation will raise a KeyError when attempted on dictionary 'M'?
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What will the function call M.values() return if 'M' contains {'K':1, 'B':2}?
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After executing D.popitem(), what will the dictionary 'D' look like given its previous state?
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Study Notes
Dictionaries in Python
- A dictionary is a data structure that stores data as key-value pairs within curly braces
{} - Each key is separated from its value by a colon
: - Multiple key-value pairs are separated by commas
, - Keys must be unique, while values can be repeated
- Dictionaries are also known as maps or associative arrays
Operations on Dictionaries
-
Adding/Updating Items:
- Use the assignment operator
=to add a new key-value pair or update an existing one - Example:
D['Marks'] = 95
- Use the assignment operator
-
Accessing Items:
- Access values by using the key within square brackets
[] - Example:
print(D['Reg'])
- Access values by using the key within square brackets
-
Deleting Items:
- Use the
delkeyword to delete specific items, for example,del(D['Name']) - Remove all items using
D.clear() - Remove a specific key-value pair and return the value with the
pop(key)method - Remove a random key-value pair and return it with the
popitem()method
- Use the
Built-in Operations on Dictionaries
-
Length:
- Use
len(M)to get the number of key-value pairs in the dictionary. - Example:
print(len (M))
- Use
-
Keys:
- Use
M.keys()to get a view of all keys in the dictionary - Example:
print(M.keys())
- Use
-
Values:
- Use
M.values()to get a view of all values in the dictionary - Example:
print(M.values())
- Use
-
Items:
- Use
M.items()to get a view of all key-value pairs as tuples - Example:
print(M.items())
- Use
Arrays in Python
- Arrays are homogenous data structures, meaning they can only store values of the same data type
- In Python, arrays can only store integers and float values
- Arrays are not built-in in Python; you need to import the
arraymodule - Lists are more commonly used in Python than arrays
Array Creation
- Use the
arraymodule to create an array - Specify the type code (e.g.,
'i'for integers,'f'for floats) and the values within square brackets[] - Example:
A = arr.array('i', [1, 2, 3, 4, 5])
Difference Between Lists and Arrays
- Lists: Heterogeneous data structures, built-in, can store various data types, including strings and characters
- Arrays: Homogeneous data structures requiring import, restricted to numbers (integers and floats)
Application of Data Structures
- Lists and tuples are used to store values of different data types
- Tuples are used for immutable data (values cannot change)
- Lists are used for flexible data that can change
- Tuples are generally faster than lists
- Tuples can be used as dictionary keys, but lists cannot
- Dictionaries are suited for scenarios where key-value relationships need to be established and maintained.
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Description
This quiz covers the fundamental concepts of dictionaries in Python, including their structure, unique keys, and methods for adding, accessing, and deleting items. Learn how to effectively manipulate dictionaries with practical examples and operations.
