[Tut] How to Get a Random Entry from a Python Dictionary

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How to Get a Random Entry from a Python Dictionary

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Problem Formulation and Solution Overview

This article will show you how to get a random entry from a Dictionary in Python.

To make it more interesting, we have the following running scenario:

The Plot: Mr. Sinclair, an 8th great Science Teacher, is giving his students a quiz on the first 25 [i]Periodic Table elements. He has asked you to write a Python script so that when run, it generates a random key, value, or key:value pair from the Dictionary shown below to ask his students.[/i]

Code:

els = {'Hydrogen': 'H', 'Helium': 'He', 'Lithium': 'Li', 'Beryllium': 'Be', 'Boron': 'B', 'Carbon': 'C', 'Nitrogen': 'N', 'Oxygen': 'O', 'Fluorine': 'F', 'Neon': 'Ne', 'Sodium': 'Na', 'Magnesium': 'Mg', 'Aluminum': 'Al', 'Silicon': 'Si', 'Phosphorus': 'P', 'Sulfur': 'S', 'Chlorine': 'Cl', 'Argon': 'Ar', 'Potassium': 'K', 'Calcium': 'Ca', 'Scandium': 'Sc', 'Titanium': 'Ti', 'Vanadium': 'V', 'Chromium': 'Cr', 'Manganese': 'Mn'}

Question: How would we write code to get a random entry from a Dictionary?

We can accomplish this task by one of the following options:

• Method 1: Use
  Code:

  random.choice()
  and
  Code:

  items()
  
  
  
• Method 2: Use
  Code:

  random.choice()
  and
  Code:

  keys()
  
  
  
• Method 3: Use
  Code:

  random.choice()
  https://blog.finxter.com/python-random-module/and
  Code:

  values()
  
  
  
• Method 4: Use
  Code:

  sample()
  
  
  
• Method 5: Use
  Code:

  np.random.choice()
  
  

Preparation

This article uses the

Code:

random

library for each example. For these code samples to run error-free, add the following snippet to the top of each example.

Code:

import random

Method 1: Use random.choice() and items()

This example uses

Code:

random.choice()

and

Code:

items()

to generate a random Dictionary key:value pair.

Code:

el_list = list(els.items()) random_el = random.choice(el_list) print(random_el)

The above code converts the Dictionary of Periodic Table Elements to a List of Tuples and saves it to

Code:

el_list

. If output to the terminal, the contents of

Code:

el_list

contains the following.

Code:

[('Hydrogen', 'H'), ('Helium', 'He'), ('Lithium', 'Li'), ('Beryllium', 'Be'), ('Boron', 'B'), ('Carbon', 'C'), ('Nitrogen', 'N'), ('Oxygen', 'O'), ('Fluorine', 'F'), ('Neon', 'Ne'), ('Sodium', 'Na'), ('Magnesium', 'Mg'), ('Aluminum', 'Al'), ('Silicon', 'Si'), ('Phosphorus', 'P'), ('Sulfur', 'S'), ('Chlorine', 'Cl'), ('Argon', 'Ar'), ('Potassium', 'K'), ('Calcium', 'Ca'), ('Scandium', 'Sc'), ('Titanium', 'Ti'), ('Vanadium', 'V'), ('Chromium', 'Cr'), ('Manganese', 'Mn')]

Next,

Code:

random.choice()

is called and passed one (1) argument:

Code:

el_list

.

The results return a random

Code:

Tuple

from the List of Tuples, saves to

Code:

random_el

and is output to the terminal.

Code:

('Oxygen', 'O')

This code can be streamlined down to the following.

Code:

random_el = random.choice(list(els.items()))

Method 2: Use random.choice() and keys()

This example uses

Code:

random.choice()

and

Code:

keys()

to generate a random Dictionary key.

Code:

random_el = random.choice(list(els.keys())) print(random_el)

The above code calls

Code:

random.choice()

and passes it one (1) argument: the keys of the

Code:

els

Dictionary converted to a List of Tuples.

The result returns a random key, saves to

Code:

random_el

and is output to the terminal.

Code:

Beryllium

Method 3: Use random.choice() and dict.values()

This example uses

Code:

random.choice()

and

Code:

values()

to generate a random Dictionary value.

Code:

random_el = random.choice(list(els.values())) print(random_el)

The above code calls

Code:

random.choice()

and passes it one (1) argument: the keys of the

Code:

els

Dictionary converted to a

Code:

List of Tuples

.

The result returns a random value, saves to

Code:

random_el

and is output to the terminal.

Code:

Si

Method 4: Use sample()

This example uses the

Code:

sample()

function to generate a random Dictionary key.

Code:

from random import sample random_el = sample(list(els), 1) print(random_el)

The above code requires

Code:

sample

to be imported from the

Code:

random

library.

Then,

Code:

sample()

is called and passed two (2) arguments:

Code:

els

converted to a

Code:

List of Tuples

and the number of random keys to return.

The results save to

Code:

random_el

and is output to the terminal.

Code:

['Carbon']

Method 5: Use np.random.choice()

This example uses NumPy and

Code:

np.random.choice()

to generate a random Dictionary key.

Before moving forward, please ensure the NumPy library is installed. Click here if you require instructions.

Code:

import numpy as np random_el = np.random.choice(list(els), 1) print(random_el)

This code imports the NumPy library installed above.

Then,

Code:

np.random.choice()

is called and passed two (2) arguments:

Code:

els

converted to a List of Tuples and the number of random keys to return.

The results save to

Code:

random_el

and is output to the terminal.

Code:

['Chromium' 'Silicon' 'Oxygen']

Note: https://docs.python.org/3/library/random.html

Code:

np.random.choice()

has an additional parameter that can be passed. This parameter is a

Code:

List

containing associated probabilities.

Bonus:

This code generates a random key:value pair from a list of tuples. When the teacher runs this code, a random question displays on the screen and waits for a student to answer. Press 1 to display the answer, 2 to quit.

Code:

import keyboard import random import time els = {'Hydrogen': 'H', 'Helium': 'He', 'Lithium': 'Li', 'Beryllium': 'Be', 'Boron': 'B', 'Carbon': 'C', 'Nitrogen': 'N', 'Oxygen': 'O', 'Fluorine': 'F', 'Neon': 'Ne', 'Sodium': 'Na', 'Magnesium': 'Mg', 'Aluminum': 'Al', 'Silicon': 'Si', 'Phosphorus': 'P', 'Sulfur': 'S', 'Chlorine': 'Cl', 'Argon': 'Ar', 'Potassium': 'K', 'Calcium': 'Ca', 'Scandium': 'Sc', 'Titanium': 'Ti', 'Vanadium': 'V', 'Chromium': 'Cr', 'Manganese': 'Mn'} print('1 Answer 2 quit') def quiz(): while True: k, v = random.choice(list(els.items())) print(f'\nWhat is the Symbol for {k}?') pressed = keyboard.read_key() if pressed == '1': print(f'The answer is {v}!') elif pressed == '2': print("Exiting\n") exit(0) time.sleep(5) quiz()

Finxter Challenge!
Write code to allow the teacher to enter the answer!

Summary

This article has provided five (5) ways to get a random entry from a Dictionary to select the best fit for your coding requirements.

Good Luck & Happy Coding!

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