Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How to convert a dictionary to a matrix or nArray in Python?
In this article, we will show you how to convert a dictionary to a matrix or a NumPy array using the array() function of the NumPy library in python.
It is sometimes necessary to convert a dictionary in Python into a NumPy array, and Python provides an efficient way of doing so. Converting a dictionary to a NumPy array gives an array containing the key-value pairs in the dictionary.
In this section, we will look at examples of converting various types of dictionaries to a NumPy array in Python
- Converting a Dictionary to a Numpy Array
- Converting a Nested Dictionary to a Numpy Array
- Converting a Dictionary with Mixed keys to a Numpy Array
numpy.array() function
It returns a ndarray. The ndarray is an array object that satisfies the given requirements.
To convert a dictionary into a NumPy array, Python has the numpy.array() method, but we must first perform some preliminary work. Follow these three basic steps as a pre-task.
- First, use dict.items() to get a group of the key-value pairs in the dictionary.
- Then, having this group as an object, use list(obj) to convert it to a list.
- Finally, using this list as data, call numpy.array(data) to convert it to an array.
Syntax
numpy.array(object, dtype = None, *, copy = True, order = ‘K’, subok = False, ndmin = 0)
parameters
object − this is an array or any object that exposes the array interface.
dtype − The array's preferred data type.
copy − If true (which is the default), the item is copied. Otherwise, a copy will only be produced if __array__ returns a copy
order − It represents the memory layout of the array
subok − If true, sub-classes are passed through; otherwise, the returned array is forced to be a base-class array (default)
ndmin − Indicates the minimum number of dimensions for the resultant array.
Return Value − returns a ndarray(it is an array object that satisfies the specified requirements)
Converting a Dictionary to a Numpy Array
Algorithm (Steps)
Following are the Algorithm/steps to be followed to perform the desired task −
Use the import keyword, to import the numpy module with an alias name(np).
Create a variable to store an input dictionary.
Apply the items() function(returns a group of the key-value pairs in the dictionary) on the input dictionary to get all the key-value pairs in the dictionary and create a variable to store it.
Use the list() function(returns a list of an iterable), to convert all the key-value pairs of the dictionary to list data type.
Use the array() function(returns a ndarray. The ndarray is an array object that satisfies the given requirements) of NumPy module to convert the above list of data to a NumPy array.
Print the resultant NumPy array of the input dictionary after conversion.
Example
The following program converts the input dictionary to a NumPy array using the array() function and returns it −
# importing numpy module with an alias name import numpy as np # creating a dictionary inputDict = {1: 'Hello', 2: 'Tutorialspoint', 3: 'python'} # getting all the key-value pairs in the dictionary result_keyvalpairs = inputDict.items() # converting an object to a list list_data = list(result_keyvalpairs) # converting list to an numpy array using numpy array() function numpy_array = np.array(list_data) print("Input Dictionary =",inputDict) # printing the resultant numpy array print("The resultant numpy array:\n", numpy_array)
Output
On executing, the above program will generate the following output
Input Dictionary = {1: 'Hello', 2: 'Tutorialspoint', 3: 'python'}
The resultant numpy array:
[['1' 'Hello']
['2' 'Tutorialspoint']
['3' 'python']]
Converting a Nested Dictionary to a Numpy Array
Algorithm (Steps)
Following are the Algorithm/steps to be followed to perform the desired task −
Create a variable to store an input nested dictionary(dictionary within another dictionary).
Use the list() function(returns a list of an iteratable), to convert all the nested key-value pairs of the dictionary to list data type.
Use the array() function of NumPy module to convert the above list of data to a NumPy array.
Print the resultant NumPy array of the input dictionary after conversion.
Example
The following program converts the nested input dictionary to a NumPy array using the array() function and returns it
# importing NumPy module with an alias name import numpy as np # creating a nested dictionary nestedDictionary = {1: 'Hello', 2: 'Tutorialspoint', 3: {'X': 'This is', 'Y': 'python', 'Z': 'code'}} # getting all the key-value pairs in the dictionary result_keyvalpairs = nestedDictionary.items() # converting an object to a list list_data = list(result_keyvalpairs) # converting list to an array using numpy array() function numpy_array = np.array(list_data) print("Input nested Dictionary = ",nestedDictionary) # printing the resultant numpy array print("\nThe resultant numpy array:\n", numpy_array)
Output
On executing, the above program will generate the following output
Input nested Dictionary = {1: 'Hello', 2: 'Tutorialspoint', 3: {'X': 'This is', 'Y': 'python', 'Z': 'code'}}
The resultant numpy array:
[[1 'Hello']
[2 'Tutorialspoint']
[3 {'X': 'This is', 'Y': 'python', 'Z': 'code'}]]
Converting a Dictionary with Mixed keys to a Numpy Array
Create an input dictionary with mixed keys such as string, integer, float, list, and so on, and fill it with random values.
Example
The following program converts a dictionary with Mixed keys to a NumPy array using the array() function and returns it −
# importing numpy module with an alias name import numpy as np # creating a dictionary with mixed keys(like string and numbers as keys) nestedDictionary = {'website': 'Tutorialspoint', 10: [2, 5, 8]} # getting all the key-value pairs in the dictionary result_keyvalpairs = nestedDictionary.items() # converting an object to a list list_data = list(result_keyvalpairs) # converting list to an array using numpy array() function numpy_array = np.array(list_data, dtype=object) # printing the resultant numpy array print("The resultant numpy array:\n", numpy_array)
Output
On executing, the above program will generate the following output
The resultant numpy array: [['website' 'Tutorialspoint'] [10 list([2, 5, 8])]]
Conclusion
We learned about the various types of key value pairs in dictionaries and how to convert them to matrices or Numpy Arrays in Python in this article.
16K+ Views
