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Calculate standard deviation of a dictionary in Python
  • Last Updated : 01 Nov, 2020

Python dictionary is a versatile data structure that allows a lot of operations to be done without any hassle. Calculating the standard deviation is shown below.

Example #1: Using numpy.std()

First, we create a dictionary. Then we store all the values in a list by iterating over it. After this using the NumPy we calculate the standard deviation of the list.

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# imporitng numpy
import numpy as np
      
# creating our test dictionary
dicti = {'a': 20, 'b': 32, 'c': 12, 'd': 93, 'e': 84}
      
# declaring an empty list
listr = []
      
# appending all the values in the list
for value in dicti.values():
    listr.append(value)
          
# calculating standard deviation using np.std
std = np.std(listr)
      
# printing results
print(std)

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Output: 



33.63569532505609  

Example #2: Using list comprehension

First, we create a list of values from the dictionary using a loop. Then we calculate mean, variance and then the standard deviation.

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# creating our test dictionary
dicti = {'a': 20, 'b': 32, 'c': 12, 'd': 93, 'e': 84}
  
# declaring an empty list
listr = []
  
# appending all the values in the list
for value in dicti.values():
    listr.append(value)
  
# Standard deviation of list
# Using sum() + list comprehension
mean = sum(listr) / len(listr)
variance = sum([((x - mean) ** 2) for x in listr]) / len(listr)
res = variance ** 0.5
print(res)

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Output: 

33.63569532505609  

Example #3: Using pstdev()

Pythons inbuilt statistics library provides a function to compute the standard deviation of a given list.

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# importing the module
import statistics
  
# creating the test dictionary
dicti = {'a': 20, 'b': 32, 'c': 12, 'd': 93, 'e': 84}
  
# declaring an empty list
listr = []
  
# appending all the values in the list
for value in dicti.values():
    listr.append(value)
  
# Standard deviation of list
# Using pstdev()
res = statistics.pstdev(listr)
print(res)

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Output

33.63569532505609

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