Dictionary Comprehension

Last Updated: 07-11-2017

Python Dictionary Comprehension

Like List Comprehension, Python allows dictionary comprehensions. We can create dictionaries using simple expressions. A dictionary comprehension takes the form {key: value for (key, value) in iterable}

Let’s see a example,lets assume we have two lists named keys and value now,

# Python code to demonstrate dictionary 
# comprehension 

# Lists to represent keys and values 
keys = ['a','b','c','d','e'] 
values = [1,2,3,4,5] 

# but this line shows dict comprehension here 
myDict = { k:v for (k,v) in zip(keys, values)} 

# We can use below too 
# myDict = dict(zip(keys, values)) 

print (myDict)

Output :

{'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}

We can also make dictionary from a list using comprehension

# Python code to demonstrate dictionary 
# creation using list comprehension 
myDict = {x: x**2 for x in [1,2,3,4,5]} 
print (myDict)

Output :

{1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

and like,

sDict = {x.upper(): x*3 for x in 'coding '} 
print (sDict)

Output :

{'O': 'ooo', 'N': 'nnn', 'I': 'iii', 'C': 'ccc', 'D': 'ddd', 'G': 'ggg'}

We can use Dictionary comprehensions with if and else statements and with other expressions too. This example below maps the numbers to their cubes that are not divisible by 4:

# Python code to demonstrate dictionary 
# comprehension using if. 
newdict = {x: x**3 for x in range(10) if x**3 % 4 == 0} 
print(newdict)

Output :

{0: 0, 8: 512, 2: 8, 4: 64, 6: 216}

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