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Questions and Answers
What is the primary purpose of a list in Python?
What is the primary purpose of a list in Python?
Which method can be used to add an item to a list in Python?
Which method can be used to add an item to a list in Python?
What distinguishes a dictionary from a list in Python?
What distinguishes a dictionary from a list in Python?
In what scenario would a dictionary be more appropriate than a list?
In what scenario would a dictionary be more appropriate than a list?
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Which of the following statements about list traversals is true?
Which of the following statements about list traversals is true?
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What does the 'in' operator do when applied to a list?
What does the 'in' operator do when applied to a list?
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How is an element replaced in a list?
How is an element replaced in a list?
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What does the == operator return when comparing two variables in Python?
What does the == operator return when comparing two variables in Python?
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What is the outcome of the following code? numbers = [2, 3, 4, 5]; for index in range(len(numbers)): numbers[index] = numbers[index] ** 2;
What is the outcome of the following code? numbers = [2, 3, 4, 5]; for index in range(len(numbers)): numbers[index] = numbers[index] ** 2;
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Which statement is true about lists?
Which statement is true about lists?
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Which operator would you use in Python to check if two variables reference the same object?
Which operator would you use in Python to check if two variables reference the same object?
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What will 'words = sentence.split()' produce when applied to the string 'This example has five words.'?
What will 'words = sentence.split()' produce when applied to the string 'This example has five words.'?
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If 'first' is a list assigned as 'first = [20, 30, 40]', what will 'first is second' return if 'second' is assigned as 'second = first'?
If 'first' is a list assigned as 'first = [20, 30, 40]', what will 'first is second' return if 'second' is assigned as 'second = first'?
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What does the is operator check for in Python?
What does the is operator check for in Python?
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Given the statements 'first = [20, 30, 40]' and 'third = list(first)', what will 'first is third' evaluate to?
Given the statements 'first = [20, 30, 40]' and 'third = list(first)', what will 'first is third' evaluate to?
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What does the method L.append(element) do?
What does the method L.append(element) do?
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Which method can be used to add elements from another list to the end of a list?
Which method can be used to add elements from another list to the end of a list?
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What happens when you use L.insert(index, element) with an index greater than the length of L?
What happens when you use L.insert(index, element) with an index greater than the length of L?
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What is the purpose of the L.pop() method?
What is the purpose of the L.pop() method?
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If you execute 'example.insert(1, 10)' on the list 'example = [1, 2]', what will the list look like afterward?
If you execute 'example.insert(1, 10)' on the list 'example = [1, 2]', what will the list look like afterward?
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A list allows the programmer to manipulate a sequence of data values of any types.
A list allows the programmer to manipulate a sequence of data values of any types.
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A dictionary organizes data values by their sequential position.
A dictionary organizes data values by their sequential position.
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Lists and dictionaries are not useful for organizing data in programming applications.
Lists and dictionaries are not useful for organizing data in programming applications.
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Methods can be used to manipulate both lists and dictionaries in Python.
Methods can be used to manipulate both lists and dictionaries in Python.
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Functions that expect parameters and return values are not part of Python's capabilities.
Functions that expect parameters and return values are not part of Python's capabilities.
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When using the split method on a sentence, it divides the sentence into individual characters.
When using the split method on a sentence, it divides the sentence into individual characters.
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The expression '3 in [1, 2, 3]' will return false.
The expression '3 in [1, 2, 3]' will return false.
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The result of the operation 'numbers[index] = numbers[index] ** 2' on the list [2, 3, 4, 5] will be [4, 9, 16, 25].
The result of the operation 'numbers[index] = numbers[index] ** 2' on the list [2, 3, 4, 5] will be [4, 9, 16, 25].
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A list in Python is mutable, meaning its elements can be changed after creation.
A list in Python is mutable, meaning its elements can be changed after creation.
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In Python, the 'in' operator can be used to check for the presence of an element within a list.
In Python, the 'in' operator can be used to check for the presence of an element within a list.
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The method L.append(element) removes an element from the end of L.
The method L.append(element) removes an element from the end of L.
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The insert method can insert an element at any index if the index is less than the length of the list.
The insert method can insert an element at any index if the index is less than the length of the list.
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Using L.pop() without an index removes the first element of the list.
Using L.pop() without an index removes the first element of the list.
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L.extend(aList) adds the elements of aList to the beginning of L.
L.extend(aList) adds the elements of aList to the beginning of L.
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The method pop can only remove the last element of a list.
The method pop can only remove the last element of a list.
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If an index is greater than the length of the list, L.insert(index, element) inserts the element at the end of the list.
If an index is greater than the length of the list, L.insert(index, element) inserts the element at the end of the list.
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The method extend adds elements from another list to the end of the current list.
The method extend adds elements from another list to the end of the current list.
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The in operator returns the position of an element in a list.
The in operator returns the position of an element in a list.
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The method index raises an error when the target element is not found in the list.
The method index raises an error when the target element is not found in the list.
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The append method can be used to add multiple elements to a list at once.
The append method can be used to add multiple elements to a list at once.
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Study Notes
Fundamentals of Python: First Programs - Second Edition
- Chapter 5 is titled "Lists and Dictionaries"
- Objectives of Chapter 5
- Construct lists and access items in those lists
- Use methods to manipulate lists
- Perform traversals of lists to process items in the lists
- Define simple functions that expect parameters and return values
- Construct dictionaries and access entries in those dictionaries
- Use methods to manipulate dictionaries
- Determine whether a list or a dictionary is an appropriate data structure for a given application
Introduction
- Lists allow programmers to work with sequences of any data type.
- Dictionaries associate data values with other data values, rather than by sequential position.
- Lists and dictionaries are powerful tools for organizing data in applications.
Lists
- Lists are sequences of data values (items or elements)
- Examples include shopping lists, to-do lists, athletic team rosters, guest lists, recipes, text documents, and phone books.
- Each item in a list has a unique index that specifies its position from 0 to length minus 1.
List Literals and Basic Operators
- Lists can contain expressions.
- Lists of integers can be generated using range.
- The list function can build a list from any iterable sequence.
- len, [], +, and == operators work as expected on lists.
Replacing an Element in a List
- Lists are mutable; elements can be inserted, removed, or replaced.
- The subscript operator is used to replace elements.
- The example shows how to replace each number in a list with its square.
- Strings can be split to extract lists of words.
List Methods
- Methods for inserting/removing elements include append(element), extend(aList), insert(index, element), pop(), pop(index).
- The method insert expects an integer index and the new element.
- Methods append and extend add elements to the end of a list.
- Pop removes and returns elements.
- The method pop is used to remove an element at a given position.
Searching a List
- The in operator determines an element's presence or absence in a list but does not return its position.
- The index method locates an element's position in a list.
Sorting a List
- A list's elements are ordered by position, but a natural ordering can be imposed (e.g., alphabetical order).
- The sort method modifies a list by arranging elements in ascending order.
Mutator Methods and the Value None
- Mutator methods, such as insert, append, extend, pop, and sort, typically do not return a specific value.
- Python automatically returns the special value None from these methods.
Aliasing and Side Effects
- The mutable nature of lists leads to aliasing,
- Two variables referencing the exact same list object.
- Creating a new object to copy the contents of a list avoids issues
Equality: Object Identity and Structural Equivalence
- The == operator checks for structural equivalence(same contents) or object identity (identical object).
- The is operator checks for object identity.
Example: Using a List to Find the Median of a Set of Numbers
- A Python code example demonstrates how to read numbers from a file, sort them, and calculate the median.
Tuples
- Tuples resemble lists, but they are immutable.
- Elements are enclosed in parentheses.
- Using + operator to concatenate tuples.
Defining Simple Functions
- Functions organize code, making scripts more efficient.
The Syntax of Simple Function Definitions
- Function definitions consist of a header and a body.
- Docstrings explain a function's purpose.
Parameters and Arguments
- Parameters are the names in the function definition.
- Arguments are the values passed. These values must match the parameters in number and positions.
The Return Statement
- A return statement explicitly returns a value from a function.
- If no return, Python automatically returns None.
Boolean Functions
- Boolean functions test arguments for a property, returning True if the property exists, False if not.
Defining a Main Function
- The main function is the entry point of a Python script.
Dictionaries
- Dictionaries associate a set of keys with data values (key/value pairs ).
- Key/value entries are separated by commas, enclosed within curly braces, with a colon separating the key and value.
- Example - use cases such as phone books and personal information.
Adding Keys and Replacing Values
- Use square brackets to add or replace key/value pairs in a dictionary.
Accessing Values
- Use square brackets
[]to access the value associated with a given key. - Use the
has_keymethod or thegetmethod to check for the existence of a key.
Removing Keys
- Use the
popmethod to remove a key/value pair from a dictionary.
Traversing a Dictionary
- Looping through the key/value pairs to retrieve or print them.
- Items() method can be used to generate an iterator of (key,value) tuples from the dictionary.
Chapter Summary
- Lists are ordered, mutable sequences.
- Tuples are similar to lists but are immutable.
- Functions consist of a header and body; a return statement returns a value. Dictionaries associate keys with values.
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Description
Explore Chapter 5 of 'Fundamentals of Python: First Programs - Second Edition' focusing on lists and dictionaries. Learn how to construct and manipulate lists, as well as how to define and use dictionaries for effective data management. This chapter equips you with essential skills for organizing data in Python applications.
