# Mastering Data Manipulation with NumPy Arrays: Converting Lists to Arrays

In the world of programming, working with data is an incredibly crucial aspect of the job. It involves handling and manipulating it in ways that are useful for our programs.

One commonly used tool for this job is NumPy, a Python library for scientific computing. It provides a powerful array infrastructure for fast calculation and data analysis.

In this article, we will explore one of the basic tasks when working with data in NumPy – converting a list to a NumPy array. We will first introduce the syntax for this conversion before working our way through two examples.

Finally, we will provide additional resources for further learning. Converting a List to NumPy Array:

We will begin by discussing the syntax for converting a list to a NumPy array.

NumPy arrays come in two types – single-dimensional (1D) arrays and multi-dimensional (2D) arrays. The conversion of a list to a NumPy array can be done in a variety of ways, depending on the desired type of array.

Syntax for Converting a List to NumPy Array:

To convert a list to a NumPy array, we first need to import NumPy.

“`

## import numpy as np

“`

Now, let’s convert a list to a 1D NumPy array using the `np.array()` function.

“`

list_1d = [1, 2, 3, 4]

array_1d = np.array(list_1d)

“`

The resulting `array_1d` will be `[1, 2, 3, 4]`.

Similarly, we can convert a list of lists to a NumPy array of arrays as follows:

“`

list_2d = [[1, 2], [3, 4], [5, 6]]

array_2d = np.array(list_2d)

“`

The resulting `array_2d` will be

“`

array([[1, 2],

[3, 4],

[5, 6]])

“`

Example 1: Convert List to NumPy Array:

Imagine that we have a list containing the temperatures in Celsius for a week. We want to convert this list to a NumPy array so that we can perform some calculations on it.

“`

temps_celsius = [15, 16, 17, 18, 19, 20, 21]

“`

To convert this list to a 1D NumPy array, we begin by importing NumPy and using the `np.array()` function. “`

## import numpy as np

temps_array = np.array(temps_celsius)

“`

Our resulting `temps_array` should now be `[15 16 17 18 19 20 21]`. Now we can perform computations on the array directly.

“`

# Converting the temperature in Celsius to Fahrenheit

temps_fahrenheit = temps_array * 9/5 + 32

>>> temps_fahrenheit

array([59. , 60.8, 62.6, 64.4, 66.2, 68.

, 69.8])

“`

Example 2: Convert List of Lists to NumPy Array of Arrays:

Now let’s consider a more complex example where we would like to convert a list of lists to a NumPy array of arrays. Consider the following list of basketball players and their heights:

“`

players_heights = [[‘Michael Jordan’, 198],

[‘Kobe Bryant’, 198],

[‘LeBron James’, 206],

[‘Shaquille O’Neal’, 216]]

“`

We can convert this list of lists to a NumPy array using the `np.array()` function.

“`

## import numpy as np

players_array = np.array(players_heights)

“`

Our resulting `players_array` should now be

“`

array([[‘Michael Jordan’, ‘198’],

[‘Kobe Bryant’, ‘198’],

[‘LeBron James’, ‘206’],

[‘Shaquille O’Neal’, ‘216’]], dtype=’

“`

Note that by default, the NumPy array will choose the data type based on the input data. In this case, it has chosen a data type of “Unicode string of maximum length 17”.

To specify the data type explicitly, we can use the `dtype` parameter. “`

players_array = np.array(players_heights, dtype=str)

“`

Our resulting `players_array` should now be

“`

array([[‘Michael Jordan’, ‘198’],

[‘Kobe Bryant’, ‘198’],

[‘LeBron James’, ‘206’],

[‘Shaquille O’Neal’, ‘216’]], dtype=’

“`