# List Comprehensions

`numbers = [1, -2, 3, -4, 5]new_nums = []for num in numbers:    if num > 0:        new_nums.append(num)print(new_nums) # prints [1, 3, 5]`
`new_nums = [num for num in numbers if num > 0]print(new_nums) # prints [1, 3, 5]`
`output_list = [expression for var in input_list if condition]`
`squares = [num * num for num in numbers] # [1, 4, 9, 16, 25]`

# Dictionary Comprehensions

## Example 1 — Creating a Dictionary from a List

`nums = [1, 2, 3, 4, 5, 6, 7, 8]dict = {}for num in nums:    if num % 2 == 0:        dict[num] = str(num)    print(dict) # prints {2: '2', 4: '4', 6: '6', 8: '8'}`
`dict = {num: str(num) for num in nums if num % 2 == 0}print(dict) # {2: '2', 4: '4', 6: '6', 8: '8'}`

## Example 2— Operating on an Existing Dictionary

`dict = {'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}`
`triple_dict = {k:v*3 for (k,v) in dict.items()}print(triple_dict) # {'a': 3, 'b': 6, 'c': 9, 'd': 12, 'e': 15}`
`{key:value for (key,value) in dict if key,value satisfy condition}`

# Set Comprehensions

`numbers = [1, 2, 3, 4, 5, 6, 7, 8]   filtered_nums = set()   for num in numbers:     if num % 2 == 0:         filtered_nums.add(num)   print(filtered_nums) # {8, 2, 4, 6} (order doesnt matter with sets)`
`filtered_nums = {num for num in numbers if num % 2 == 0}print(filtered_nums) # {8, 2, 4, 6}`

# Generator Comprehensions

`def square_even(numbers):    for number in numbers:        if number % 2 == 0:            yield(number * number)numbers = [1, 2, 3, 4, 5, 6]squared_numbers = square_even(numbers)# Print a generator:for number in squared_numbers:    print(number)# prints 4 16 36`
`squared_numbers = (num * num for num in numbers if num % 2 == 0)# Print a generator:for number in squared_numbers:     print(number)# prints 4 16 36`

# Conclusion

## CodeX

Everything connected with Tech & Code

Written by

## Artturi Jalli

Tech Expert, Entrepreneur, Software Engineer from Finland. Writing about programming and science. Check out my blog at https://www.codingem.com/

Everything connected with Tech & Code

Written by

## Artturi Jalli

Tech Expert, Entrepreneur, Software Engineer from Finland. Writing about programming and science. Check out my blog at https://www.codingem.com/

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