Introduction to Python with Google Colab

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Questions and Answers

What happens to the size of a sparse matrix when additional zero elements are added?

  • It increases in size proportionally to the number of added zeros.
  • It remains unchanged regardless of the number of added zeros. (correct)
  • It changes based on the type of sparse matrix used.
  • It becomes more efficient in storage.

Which of the following is NOT a type of sparse matrix mentioned?

  • Dense Matrix (correct)
  • Compressed Sparse Row (CSR)
  • Compressed Sparse Column
  • Dictionary of Keys

What is the index of the first element in a NumPy array?

  • Depends on the array length
  • 1
  • -1
  • 0 (correct)

What represents a sparse matrix that was created from the larger matrix in the example?

<p>It only contains non-zero elements and their positions. (C)</p> Signup and view all the answers

Which method of selecting elements in a NumPy array correctly references the second row, second column?

<p>matrix[1,1] (A)</p> Signup and view all the answers

What advantage does a sparse matrix have in terms of storage?

<p>It reduces memory usage by storing only significant values. (D)</p> Signup and view all the answers

What is a primary purpose of the 'kernels' in a Google Colab notebook?

<p>To execute code blocks in the notebook. (A)</p> Signup and view all the answers

Which of the following operations can be performed easily with NumPy arrays?

<p>Selection of elements based on conditions. (D)</p> Signup and view all the answers

Which of the following statements about Python modules is correct?

<p>The module name is derived from the file name with .py removed. (C)</p> Signup and view all the answers

Which command correctly imports a module in Python using the recommended method?

<p>import module1 as mod1 (D)</p> Signup and view all the answers

Why is it important to choose the right type of sparse matrix?

<p>Each type has different implications and performance characteristics. (C)</p> Signup and view all the answers

In NumPy, what is the outcome of executing 'np.array([1, 2, 3])'?

<p>It creates a one-dimensional row vector. (A)</p> Signup and view all the answers

What would be the output of 'print(vector_row)' if vector_row is defined as 'np.array([1, 2, 3])'?

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

Which command is used to create a column vector in NumPy?

<p>np.array([[1], [2], [3]]) (A)</p> Signup and view all the answers

What does the combination 'Shift + Tab' perform in a code cell?

<p>It brings up documentation for the function being typed. (C)</p> Signup and view all the answers

What is the primary data structure used in NumPy?

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

What will be the result of executing matrix[:,1:2] on the defined matrix?

<p>array([[2], [5], [8]]) (B)</p> Signup and view all the answers

What value is returned by matrix.size for the given matrix?

<p>12 (D)</p> Signup and view all the answers

What does the ndim attribute of a NumPy array represent?

<p>The number of dimensions of the array (C)</p> Signup and view all the answers

Using the vectorized_add_1000, what would be the output if applied to the array [[1, 2, 3], [4, 5, 6], [7, 8, 9]]?

<p>array([[1001, 1002, 1003], [1004, 1005, 1006], [1007, 1008, 1009]]) (C)</p> Signup and view all the answers

Which of the following correctly describes how to select all elements of a vector in NumPy?

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

What will the output be for vector[-1] when vector is array([1, 2, 3, 4, 5, 6])?

<p>6 (A)</p> Signup and view all the answers

What is the shape of the matrix created by np.array([[1, 2, 3, 4],[5, 6, 7, 8],[9, 10, 11, 12]])?

<p>(3, 4) (B)</p> Signup and view all the answers

Which of the following statements about NumPy's vectorize is true?

<p>It converts a function to apply to all elements of an array. (C)</p> Signup and view all the answers

What does the argument -1 represent when using the reshape function in NumPy?

<p>As many columns as needed (A)</p> Signup and view all the answers

Which command correctly finds the inverse of a matrix A using NumPy?

<p>np.linalg.inv(A) (B)</p> Signup and view all the answers

What will be the output of the command matrix.reshape(12) for a matrix of size 4x3?

<p>A 1D array with 12 elements (D)</p> Signup and view all the answers

To calculate the eigenvalues of matrix A using NumPy, which of the following commands is correct?

<p>np.linalg.eig(A) (A)</p> Signup and view all the answers

If you want to create a 2x2 matrix of ones with a border of zeros, which approach should you use?

<p>Use np.pad(np.ones((2,2)), pad_width=1, mode='constant') (D)</p> Signup and view all the answers

What will be the result of applying the operation matrix + 1000 to the following matrix: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]?

<p>array([[1001, 1002, 1003], [1004, 1005, 1006], [1007, 1008, 1009]]) (B)</p> Signup and view all the answers

What is the output of np.max(matrix) for the given matrix [[1, 2, 3], [4, 5, 6], [7, 8, 9]]?

<p>9 (D)</p> Signup and view all the answers

When using np.max(matrix, axis=0), what does the output represent?

<p>The maximum value in each column of the matrix (B)</p> Signup and view all the answers

Which of the following functions would you use to calculate the variance of the elements in a matrix?

<p>np.var() (C)</p> Signup and view all the answers

Which statement is true about reshaping a matrix using np.reshape()?

<p>The total number of elements in the new shape must equal the original shape. (A)</p> Signup and view all the answers

If you want to find the mean of the first row in the matrix [[1, 2, 3], [4, 5, 6], [7, 8, 9]], which code should you use?

<p>np.mean(matrix[0]) (A)</p> Signup and view all the answers

What is the result of np.max(matrix, axis=1) using the matrix [[1, 2, 3], [4, 5, 6], [7, 8, 9]]?

<p>array([3, 6, 9]) (B)</p> Signup and view all the answers

Which operation would you use to find the standard deviation of a matrix in NumPy?

<p>np.std() (A)</p> Signup and view all the answers

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Study Notes

Introduction to Python with Google Colab

  • Python is a high-level, interpreted programming language suitable for various applications.
  • Google Colab is an online platform that allows users to write and execute Python code via Jupyter notebooks.

Google Colab Interface

  • Kernels: The computational engine that executes code blocks.
  • Cells: Containers for code or text, including markdown and code cells.
    • Key Shortcuts:
      • Shift + Enter: Execute the current cell and move to the next.
      • Shift + Tab: View documentation for the selected function.

Modules in Python

  • A module is a file containing functions and definitions, similar to #include in C/C++.
  • Import modules to access additional functions:
    • Recommended method: import module1 as mod1.

Basics of NumPy

  • NumPy is essential for machine learning, enabling efficient operations with vectors, matrices, and arrays.

Creating Vectors

  • Vectors can be created as one-dimensional arrays using NumPy:
    • Row Vector: vector_row = np.array([1, 2, 3])
    • Column Vector: vector_column = np.array([[1], [2], [3]])

Creating Matrices

  • Use NumPy to create two-dimensional arrays (matrices).
  • Larger matrices can illustrate advantages of sparse representations. For example, a sparse matrix minimizes storage of zero elements using sparse.csr_matrix().

Selecting Elements in Arrays

  • NumPy arrays are zero-indexed.
  • Selection example:
    • Third element of vector: vector[2]
    • Element at second row, second column in a matrix: matrix[1, 1]
  • Various slicing techniques allow selection of groups of elements.

Describing Matrix Properties

  • Use attributes shape, size, and ndim to describe a matrix:
    • Shape: matrix.shape indicates rows and columns.
    • Size: matrix.size gives total elements.
    • Dimensions: matrix.ndim returns the number of matrix dimensions.

Applying Functions to Arrays

  • Functions can be applied to multiple elements using np.vectorize() or broadcasting techniques, e.g., matrix + 1000.

Finding Maximum and Minimum Values

  • Use np.max() and np.min() to find max/min values in arrays.
  • Operations can be specified along certain axes with parameters like axis=0 or axis=1.

Descriptive Statistics

  • Calculate mean, variance, and standard deviation using np.mean(), np.var(), and np.std(), respectively.

Reshaping Arrays

  • Reshape matrices while maintaining data with matrix.reshape(), ensuring the total number of elements remains unchanged.
  • Use -1 to auto-calculate dimensions.

Introduction to Linear Algebra with NumPy

  • Calculate eigenvalues and eigenvectors using np.linalg.eig().
  • Compute matrix inverses with np.linalg.inv().

Post Lab Exercises

  • Implement programs to:
    • Check if all elements in an array are non-zero.
    • Create a 2x2 matrix of ones with a border of zeros.
    • Multiply a randomly generated 4x3 matrix by a 3x5 matrix.
    • Solve a system of equations using np.linalg.solve().

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