Converting an array to a number in Python is a common task when dealing with data manipulation and mathematical operations. In this tutorial, we will learn different methods to convert arrays to numbers using Python, specifically looking at the numpy library and lists.

This tutorial assumes you have some basic understanding of Python and lists. If you’re new to Python, you can check out official Python documentation for a quick introduction.

### Method 1: Converting List to Integer

Let’s start with a simple method that involves converting a list with one element to an integer. This is useful when you have a list containing a single number as a string or an integer.

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array = ['123'] number = int(array[0]) print(number) |

**Output:**

123

### Method 2: Converting List to Integer Using join()

If you have a list with multiple elements, you can use the `join()`

method to concatenate the list elements into a single string and then convert the string to an integer.

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array = ['1', '2', '3'] number = int(''.join(array)) print(number) |

**Output:**

123

### Method 3: Converting List of Integers to a Single Integer

For a list with numbers as integers, you can use the same approach as the previous method. However, you’ll need to convert the integers to strings using the `map()`

function before joining them together.

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array = [1, 2, 3] number = int(''.join(map(str, array))) print(number) |

**Output:**

123

### Method 4: Convert Array to Number Using NumPy

For more advanced operations, we can use the popular NumPy library which provides a simple way to convert an entire array into a single number using scalar multiplication.

First, you need to install the NumPy library if you haven’t already. You can install it using pip:

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pip install numpy |

Now, let’s use NumPy to convert a 1D array to a number using scalar multiplication.

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import numpy as np array = np.array([1, 2, 3]) number = np.dot(array, 10 ** np.arange(array.size)[::-1]) print(number) |

**Output:**

123

In this code, we first import the NumPy library, create an array of elements, and then use the `np.dot()`

function to compute the dot product between the array and a power of 10 array in reverse order.

## Full code:

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# Method 1 array1 = ['123'] number1 = int(array1[0]) # Method 2 array2 = ['1', '2', '3'] number2 = int(''.join(array2)) # Method 3 array3 = [1, 2, 3] number3 = int(''.join(map(str, array3))) # Method 4 import numpy as np array4 = np.array([1, 2, 3]) number4 = np.dot(array4, 10 ** np.arange(array4.size)[::-1]) print(number1) print(number2) print(number3) print(number4) |

**Output:**

123 123 123 123

## Conclusion

In this tutorial, we have discussed different methods of converting an array to a number in Python. These methods include using basic list manipulation, join() function, and using the NumPy library. You can choose the most suitable method based on the format of the input (string or integer elements), and the requirements of the specific task you’re working on.