Python List Operations Quiz
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Questions and Answers

What is the first step to average numeric values in a list?

  • Calculate total of the values (correct)
  • Divide total of the values by which operation?
  • Use a file object’s writelines method
  • Create a list comprehension

Which method is used to write the contents of a list to a file?

  • The write method of the file object
  • The writelines method of the file object (correct)
  • The write_lines method of the file object
  • The append method of the list

How does list comprehension function in creating a new list?

  • By filtering elements based on conditional expressions
  • By using nested loops for each item
  • By iterating over an existing list and appending values to a new list (correct)
  • By iterating over elements and calculating a total

What will happen if you do not include ' ' when saving a list to a file?

<p>All list items will be concatenated in one line (B)</p> Signup and view all the answers

What allows a function to return a list's contents?

<p>By passing a reference to the list (C)</p> Signup and view all the answers

What is the primary distinction between a list and a tuple in Python?

<p>A list is mutable, while a tuple is immutable. (C)</p> Signup and view all the answers

What does the expression 'numbers * 2' return if 'numbers' is defined as follows: numbers = [1, 2, 3]?

<p>[1, 2, 3, 1, 2, 3] (D)</p> Signup and view all the answers

What happens if you attempt to insert an item at a negative index that specifies an invalid position?

<p>The item will be inserted at the beginning of the list. (B)</p> Signup and view all the answers

When iterating over a list with a for loop, which statement is true?

<p>You cannot modify elements in the list during iteration. (B)</p> Signup and view all the answers

Which method removes the first occurrence of a specified item from a list?

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

What will be the output of the following code: print(list(range(5)))?

<p>[0, 1, 2, 3, 4] (A)</p> Signup and view all the answers

How can you access the last element of a list named 'items'?

<p>items[-1] (D)</p> Signup and view all the answers

When using the sort() method, what will be the order of the items in the list after execution?

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

What occurs when you use the del statement with a valid index in a list?

<p>The element at that index is removed. (A)</p> Signup and view all the answers

What will result from executing 'print([10, 20, 30] + [40, 50])'?

<p>[10, 20, 30, 40, 50] (A)</p> Signup and view all the answers

Which index would you use to access the third element of a list?

<p>2 (A)</p> Signup and view all the answers

Which of the following methods would you use to make a copy of each element in a list to a new list?

<p>for loop (D)</p> Signup and view all the answers

What is the result of attempting to call the index() method on an item that is not present in the list?

<p>A ValueError exception is raised. (B)</p> Signup and view all the answers

Which of the following best describes 'list comprehension'?

<p>A shorthand way to create lists based on existing lists. (D)</p> Signup and view all the answers

What does the reverse() method do to a list?

<p>Reverses the order of the items in the list. (B)</p> Signup and view all the answers

What will be the effect of assigning one list to another list?

<p>Both lists will reference the same list in memory. (D)</p> Signup and view all the answers

What will be the content of len_list after executing the code str_list = ['Winken', 'Blinken', 'Nod']?

<p>[6, 7, 3] (C)</p> Signup and view all the answers

What is the primary characteristic of a tuple in Python?

<p>An immutable sequence of elements (B)</p> Signup and view all the answers

Which operation is NOT supported by tuples?

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

What is the result of executing the code list2 = [item for item in list1 if item < 10] with list1 = [1, 12, 2, 20, 3, 15, 4]?

<p>[1, 2, 3, 4] (D)</p> Signup and view all the answers

How is a two-dimensional list defined?

<p>A list that contains other lists as elements (B)</p> Signup and view all the answers

What command would you use to convert a tuple to a list?

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

Which statement about list comprehensions is true?

<p>They provide a concise way to create lists. (A)</p> Signup and view all the answers

What feature of matplotlib makes it suitable for data visualization?

<p>Provides tools for two-dimensional charts and graphs (B)</p> Signup and view all the answers

What does the len function return when applied to a list?

<p>The length of the list (A)</p> Signup and view all the answers

Which of the following methods does NOT modify the original list?

<p>index(item) (C)</p> Signup and view all the answers

What will happen if an invalid index is used to access a list element?

<p>Raises an IndexError (C)</p> Signup and view all the answers

How can you concatenate two lists in Python?

<p>Using the + operator (B)</p> Signup and view all the answers

What does list slicing with a missing 'start' index default to?

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

When using the in operator, what does it return if the item is not found in the list?

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

Which method would you use to add an item to the end of a list?

<p>append(item) (D)</p> Signup and view all the answers

Which of the following methods will raise a ValueError if the item is not found in the list?

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

What does the insert(index, item) method do?

<p>Adds an item at the specified index, shifting other items (D)</p> Signup and view all the answers

Which slicing expression extracts elements starting from index 2 to 5 from a list?

<p>list[2:5] (D)</p> Signup and view all the answers

What must be done to use the matplotlib package in Python after installing it?

<p>Import the module pyplot using an alias. (B)</p> Signup and view all the answers

Which of the following statements correctly demonstrates how to define the limits of the x-axis in a matplotlib graph?

<p>plt.xlim(1, 100) (D)</p> Signup and view all the answers

What is the first step to verify if matplotlib is installed correctly on your system?

<p>Import matplotlib and check for error messages. (A)</p> Signup and view all the answers

Which command adds a point to a line graph using the plot function?

<p>plt.plot(x, y) (B)</p> Signup and view all the answers

What does the yticks function do in matplotlib?

<p>Customizes the labels for each tick mark on the Y axis (B)</p> Signup and view all the answers

In the provided Python code, which line is responsible for displaying the line graph?

<p>plt.show() (D)</p> Signup and view all the answers

Which of the following is true about the coordinates used in the plot function?

<p>They must be equal in length. (B)</p> Signup and view all the answers

What will happen if you run the command >>> import matplotlib and receive an error message?

<p>The matplotlib package is missing or not installed. (B)</p> Signup and view all the answers

Flashcards

List in Python

A sequence of items, where the order matters. Elements can be different types.

List Element

An individual item within a list.

List Indexing

Accessing specific elements by their position. First element is 0, second is 1, and so on.

Negative Indexing

Accessing elements from the end of the list. -1 is the last element, -2 is the second to last, and so on.

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List Slicing

Extracting a portion of a list, creating a new list with selected elements.

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Repetition Operator

Creates multiple copies of a sequence by multiplying it with an integer.

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Sequence

Python data type storing items in order.

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Mutable Object

An object whose content can be changed after creation.

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IndexError

An error raised when accessing a list element using an invalid index. e.g., trying to access an index that doesn't exist.

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len() Function

Returns the total number of elements in a sequence (like a list).

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Mutable Sequence

A sequence (like a list) where its elements can be changed after creation.

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Concatenating Lists

Combining two lists into one new list.

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List Methods

Specific actions that can be performed on lists.

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append() method

Adds an element to the end of a list.

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index() method

Retrieves the index of the first occurrence of an item within a list.

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in operator

Checks if an element exists in a list.

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insert() method

Inserts an element into a list at a specific index.

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List Calculations

Performing operations on list elements. This involves using loops and variables to calculate things like totals and averages.

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Passing a List to a Function

Sending a list as an input to a function. This allows functions to process and manipulate lists.

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Saving a List to a File

Writing the contents of a list into a text file. This enables storing and retrieving list data.

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Reading a List from a File

Loading data from a text file into a list. This restores list data stored in a file.

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List Comprehension

A concise way to create a new list by iterating over an existing list. It provides a more compact and readable alternative to using traditional loops.

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index(item)

This method finds the index of the first element in a list that has the same value as 'item'. If 'item' is not found, a ValueError is raised.

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insert(index, item)

This method adds 'item' to the list at the specified 'index'. Elements at or after 'index' are shifted to make room for the new item.

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sort()

This method rearranges the elements in the list so they are in ascending order (from smallest to largest).

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remove(item)

This method removes the first occurrence of 'item' from the list. If 'item' is not in the list, a ValueError is raised.

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reverse()

This method changes the order of elements in the list, from the original order to the reverse order.

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del statement

This statement removes the element at a specific index from a list. The syntax is: del list[index].

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min and max functions

Built-in functions that find the smallest and largest values in a sequence. Take a sequence as an argument.

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Copying Lists

To create a distinct copy of a list, you need to create a new list and copy each element. Avoid simple assignment as it creates a reference to the original list, not a copy.

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Nested List

A list that contains other lists as its elements. It's like a 2D grid of data.

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Two-Dimensional Lists

A list where each element is itself a list, representing data in rows and columns.

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Tuple

An immutable sequence of elements. It's like a list but you can't change its contents once created.

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Mutable vs. Immutable

Mutable objects, like lists, can be changed after creation. Immutable objects, like tuples, cannot be altered.

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Advantages of Tuples

Tuples are faster to process than lists, are safe because they prevent accidental changes, and some operations require tuples.

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Converting Tuple to List

Use the list() function to transform a tuple into a list.

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Converting List to Tuple

Use the tuple() function to transform a list into a tuple.

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matplotlib

A Python library used for creating visually appealing plots and graphs. It provides functions to generate line graphs, scatter plots, histograms, and other types of visualizations.

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pyplot

A submodule within the matplotlib library, providing a convenient interface for creating plots. It offers functions for plotting, customizing graph appearance, and displaying the results.

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xticks() function

A function to customize the labels (text) displayed at each tick mark on the x-axis. It takes two lists as arguments: one for the positions of the tick marks and another for the corresponding labels.

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yticks() function

Similar to xticks(), but for the y-axis. It customizes the labels at each tick mark on the y-axis.

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Study Notes

Lists and Tuples

  • Lists are mutable sequences, meaning their elements can be changed after creation.
  • Tuples are immutable sequences; elements cannot be changed after creation.
  • Both are ordered collections of items.
  • Lists use square brackets [], while tuples use parentheses ().

Introduction to Lists

  • Lists are Python objects that hold various data items.
  • Each item within a list is called an element.
  • Lists can contain elements of different data types (e.g., numbers, strings).
  • The print() function displays the entire list.
  • The list() function converts certain object types to a list.

Introduction to Lists (Continued)

  • Lists can hold various data types like integers(e.g., [2, 4, 6, 8, 10]) or strings (['Molly', 'Steven', 'Will', 'Alicia', 'Adriana']).
  • A list item can be accessed using its index, starting from 0 for the first item.
  • Negative indexes access elements from the end of a list (i.e., -1 is the last item, -2 is the second last item, and so on).

The Repetition Operator and Iterating over a List

  • The * symbol is used to repeat a list or sequence a given number of times.
  • A for loop iterates through each element in a list.
  • The len() function returns the length (number of elements) of a sequence or list.

Indexing

  • An index is a numerical value specifying an element's position in a list.
  • The index of the first element is 0, the second is 1, and so on.
  • Negative indexes identify an element's position relative to the end of the list. (e.g., -1 references the last item)
  • Using invalid indexes (outsides the list's bounds) triggers an IndexError.

The len function

  • The len() function returns the number of items in a list.
  • Using len(list)-1 finds the index of the last item.
  • len() can prevent IndexError when iterating over elements with a loop.

Lists Are Mutable

  • List elements can be altered after creation.
  • Assigning a new value to a specific list element using an valid index updates the list.

Concatenating Lists

  • The + operator concatenates two lists.
  • The augmented assignment operator += is used to ad a list to another list, instead of creating a new list.

List Slicing

  • A slice extracts a segment of a sequence.
  • Syntax list[start:end].
  • start defaults to 0, end defaults to the length of the source list.
  • Slices create copies of elements, not references; modifying a slice doesn't affect the original list.
  • Slices support a step value to skip elements (e.g., list[start:end:step]).
  • Negative indexes count from the end of the list.

Finding Items in Lists with the in Operator

  • The in operator checks if a value exists within a list.
  • The not in operator checks if a value doesn't exist within a list.

List Methods and Useful Built-in Functions

  • append(item) adds an item to the end of a list.
  • index(item) returns the index of the first occurrence of item in a list (raises ValueError if not found).
  • insert(index, item) inserts item at the specified index.
  • sort() sorts the list elements in ascending order.
  • remove(item) removes the first occurrence of item.
  • reverse() reverses the list's order.
  • del list[i] removes an element at a specific index.
  • min(list) returns the item with the lowest value.
  • max(list) returns the item with the highest value.

Two-Dimensional Lists

  • A two-dimensional list (nested list) is a list of lists.
  • Useful for representing tables or matrices.
  • Access elements using two indexes (row, column).

Tuples

  • Tuples are immutable sequences; elements are fixed after creation.
  • A tuple is defined using parentheses () instead of square brackets [].
  • Tuples support indexing, slicing, len(), min(), max(), and the in operator, but not the methods like append, insert, sort, or remove.
  • Be sure to include a trailing comma when the tuple contains one element to avoid confusion with a simple expression (e.g., my_tuple = (1,)).

Converting Tuples to Lists

  • Use list() to convert a tuple to a list.
  • The resultant list can be modified unlike the source tuple.

matplotlib

  • The matplotlib package provides functions for creating charts and graphs.
  • Install matplotlib separately from the standard Python library.
  • Use methods like plt.plot(), plt.bar(), and plt.pie() for various types of plotting.

Plotting a Line Graph

  • plt.plot(Xaxis_data, Yaxis_data) connects data points to create a line.
  • plt.show() displays the graph.
  • Use xlim() and ylim() to set axes limits.
  • Use xticks() and yticks() to control tick marks and labels.

Plotting a Bar Chart

  • plt.bar() can be used to create bar charts.
  • plt.show() displays the chart.
  • bar_width, and tuple of color codes parameters (color) can customize the chart.

Plotting Pie Charts

  • plt.pie() function creates a pie chart.
  • Values are interpreted as percentages of the whole.
  • labels parameter helps to label specific segments.

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Python Lists and Tuples - CSM2170 PDF

Description

Test your knowledge on Python list operations with this quiz. It covers topics such as averaging numeric values, writing lists to files, and the functionality of list comprehension. Challenge yourself to see how well you understand these fundamental concepts in Python programming.

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