NumPy Tutorial: Arrays, Properties & Operations

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Questions and Answers

Which NumPy function is used to create an array with random values between 0 and 1?

np.array()
np.randint()
np.arange()
np.random.rand() (correct)

The `np.arange()` function includes the end value in the generated array.

False (B)

What attribute of a NumPy array returns its dimensions?

shape

To change the dimensions of an NumPy array, you can use the `______` method.

reshape

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When using the `sum()` function on a NumPy array, what does the `axis` parameter control?

The direction along which the sum is calculated. (D)

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The `np.polyld()` function can only be used with NumPy arrays containing integer values.

False (B)

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What function is used to write a NumPy array to a text file?

savetxt()

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To read data from a text file into a NumPy array, use the `______` function.

loadtxt()

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What function should you use to find the number of elements in a NumPy array?

np.size (A)

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The `np.fromfile()` method can save a NumPy array to a file.

False (B)

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Given `arr = np.arange(1, 10)`, what values will `arr` contain?

[1, 2, 3, 4, 5, 6, 7, 8, 9] (C)

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What is the outcome of running `arr = np.array([1, 2, 3, 4]); arr.reshape(2, 2)`?

A 2D array with shape (2, 2): <code>[[1, 2], [3, 4]]</code> (C)

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With `arr = np.array([1, 5, 2, 9, 3])`, what NumPy function returns the maximum value present in `arr`?

amax() or max()

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By default, NumPy's `savetxt()` function saves data in binary format.

False (B)

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In `np.random.randint(1, 12, size=(3, 4))`, the array created will contain integers ranging from to .

1, 11

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Match the following NumPy functions with their descriptions:

np.array() = Creates an array from a list or tuple np.arange() = Creates an array with a range of numbers np.reshape() = Changes the shape of an array np.sum() = Calculates the sum of array elements

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Given `arr = np.array([[1, 2, 3], [4, 5, 6]])`, what will `arr.sum(axis=0)` return?

[5, 7, 9] (C)

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NumPy's `reshape()` method modifies the array in place.

False (B)

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If `arr = np.array([1, 2, 3, 4, 5])`, how can you extract the elements from index 1 up to (but not including) index 4?

arr[1:4]

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To represent the polynomial $x^2 - 2x + 3$ using NumPy, you would use `np.polyld(np.array([1, -2, 3]))`. The coefficients are listed in order of ______ power.

decreasing

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Flashcards

np.array()

Creates a NumPy array with the specified elements.

np.arange(start, stop)

Creates a NumPy array with a range of numbers.

np.random.rand(rows, cols)

Creates an array with random values between 0 and 1.

np.random.randint(low, high, size)

Creates an array with random integers within a specified range.

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array.size

Returns the number of elements in the array.

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array.shape

Returns the dimensions of the array (rows, columns).

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array.reshape(rows, cols)

Changes the shape of an array without changing its data.

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array[start_row:end_row, start_col:end_col]

Accesses specific elements or subarrays within an array.

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array.sum()

Calculates the sum of array elements.

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array.sum(axis=0 or 1)

Calculates the sum along a specified axis (0 for columns, 1 for rows).

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array.max()

Finds the maximum value in an array.

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np.polyld(array)

Defines a polynomial function from an array of coefficients.

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np.savetxt()

Saves an array to a text file.

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np.loadtxt()

Loads data from a text file into an array.

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array.tofile()

Saves an array to a binary file.

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array.fromfile()

Loads data from a binary file into an array.

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Study Notes

NumPy Library

NumPy is imported as np.

Array Creation

np.array([1,2,3,4]) creates an array with the specified values.
np.arange(1,10) generates a range of numbers from 1 to 9.
np.random.rand(3,4) produces a 3x4 array with random values between 0 and 1.
np.random.randint(1,12, size=(3,4)) creates a 3x4 array with random integers from 1 to 11.

Array Properties and Manipulation

arr4.size returns the total number of elements in the array (e.g., 12).
arr4.shape returns the dimensions of the array as a tuple (e.g., (3,4)).
ar4.reshape(4,3) changes the dimensions of the array to 4x3.
np.random.randint(1,25, size=(2,3,4)) creates a 3D array, with order 3D -> 2D -> 1D.
np.arange(1,25).reshape(2,3,4) reshapes a range into a 2x3x4 array.
ar5[0,0:2,1:3] accesses a specific slice of the array.

Array Operations

ar5.sum() calculates the sum of all elements in the array.
ar5.sum(axis=0) sums the values vertically.
ar5.sum(axis=1) sums the values horizontally.
ar5.max() finds the maximum value in the array.
ar5.max(axis = 0) finds the maximum values along axis 0.
ar5.max(axis = 1) finds the maximum values along axis 1.

Mathematical Functions

ar6 = np.array([1,-2,3]) creates an array of coefficients.
f = np.polyld(ar6) defines a polynomial function using the coefficients in ar6 (e.g., x**2 - 2x + 3).

File I/O

np.savetxt() saves array data to a file, with parameters for path, filename, data, format, and delimiter.
np.loadtxt() loads array data from a file, with parameters for path and filename.
ar5.fromfile() reads data from a file to create an array.
ar5.tofile() writes array data to a file.

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Podcast

Questions and Answers

Which NumPy function is used to create an array with random values between 0 and 1?

The np.arange() function includes the end value in the generated array.

What attribute of a NumPy array returns its dimensions?

To change the dimensions of an NumPy array, you can use the ______ method.

When using the sum() function on a NumPy array, what does the axis parameter control?

The np.polyld() function can only be used with NumPy arrays containing integer values.

What function is used to write a NumPy array to a text file?

To read data from a text file into a NumPy array, use the ______ function.

What function should you use to find the number of elements in a NumPy array?

The np.fromfile() method can save a NumPy array to a file.

Given arr = np.arange(1, 10), what values will arr contain?

What is the outcome of running arr = np.array([1, 2, 3, 4]); arr.reshape(2, 2)?

With arr = np.array([1, 5, 2, 9, 3]), what NumPy function returns the maximum value present in arr?

By default, NumPy's savetxt() function saves data in binary format.

In np.random.randint(1, 12, size=(3, 4)), the array created will contain integers ranging from __ to __.

Match the following NumPy functions with their descriptions:

Given arr = np.array([[1, 2, 3], [4, 5, 6]]), what will arr.sum(axis=0) return?

NumPy's reshape() method modifies the array in place.

If arr = np.array([1, 2, 3, 4, 5]), how can you extract the elements from index 1 up to (but not including) index 4?

To represent the polynomial $x^2 - 2x + 3$ using NumPy, you would use np.polyld(np.array([1, -2, 3])). The coefficients are listed in order of ______ power.

Flashcards

np.array()

np.arange(start, stop)

np.random.rand(rows, cols)

np.random.randint(low, high, size)

array.size

array.shape

array.reshape(rows, cols)

array[start_row:end_row, start_col:end_col]

array.sum()

array.sum(axis=0 or 1)

array.max()

np.polyld(array)

np.savetxt()

np.loadtxt()

array.tofile()

array.fromfile()

Study Notes

NumPy Library

Array Creation

Array Properties and Manipulation

Array Operations

Mathematical Functions

File I/O

Studying That Suits You

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The `np.arange()` function includes the end value in the generated array.

To change the dimensions of an NumPy array, you can use the `______` method.

When using the `sum()` function on a NumPy array, what does the `axis` parameter control?

The `np.polyld()` function can only be used with NumPy arrays containing integer values.

To read data from a text file into a NumPy array, use the `______` function.

The `np.fromfile()` method can save a NumPy array to a file.

Given `arr = np.arange(1, 10)`, what values will `arr` contain?

What is the outcome of running `arr = np.array([1, 2, 3, 4]); arr.reshape(2, 2)`?

With `arr = np.array([1, 5, 2, 9, 3])`, what NumPy function returns the maximum value present in `arr`?

By default, NumPy's `savetxt()` function saves data in binary format.

In `np.random.randint(1, 12, size=(3, 4))`, the array created will contain integers ranging from to .

Given `arr = np.array([[1, 2, 3], [4, 5, 6]])`, what will `arr.sum(axis=0)` return?

NumPy's `reshape()` method modifies the array in place.

If `arr = np.array([1, 2, 3, 4, 5])`, how can you extract the elements from index 1 up to (but not including) index 4?

To represent the polynomial $x^2 - 2x + 3$ using NumPy, you would use `np.polyld(np.array([1, -2, 3]))`. The coefficients are listed in order of ______ power.