Python: Groups the elements of a given list based on the given function
Python dictionary: Exercise-69 with Solution
Write a Python program to group the elements of a given list based on the given function.
- Use collections.defaultdict to initialize a dictionary.
- Use fn in combination with a for loop and dict.append() to populate the dictionary.
- Use dict() to convert it to a regular dictionary.
Sample Solution:
Python Code:
from collections import defaultdict
from math import floor
def test(lst, fn):
d = defaultdict(list)
for el in lst:
d[fn(el)].append(el)
return dict(d)
nums = [7,23, 3.2, 3.3, 8.4]
print("Original list & function:")
print(nums," Function name: floor:")
print("Group the elements of the said list based on the given function:")
print(test(nums, floor))
print("\n")
print("Original list & function:")
colors = ['Red', 'Green', 'Black', 'White', 'Pink']
print(colors," Function name: len:")
print("Group the elements of the said list based on the given function:")
print(test(colors, len))
Sample Output:
Original list & function: [7, 23, 3.2, 3.3, 8.4] Function name: floor: Group the elements of the said list based on the given function: {7: [7], 23: [23], 3: [3.2, 3.3], 8: [8.4]} Original list & function: ['Red', 'Green', 'Black', 'White', 'Pink'] Function name: len: Group the elements of the said list based on the given function: {3: ['Red'], 5: ['Green', 'Black', 'White'], 4: ['Pink']}
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Previous: Write a Python program to combines two or more dictionaries, creating a list of values for each key.
Next: Write a Python program to map the values of a given list to a dictionary using a function, where the key-value pairs consist of the original value as the key and the result of the function as the value.
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Python: Tips of the Day
Find current directory and file's directory:
To get the full path to the directory a Python file is contained in, write this in that file:
import os dir_path = os.path.dirname(os.path.realpath(__file__))
(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)
To get the current working directory use
import os cwd = os.getcwd()
Documentation references for the modules, constants and functions used above:
- The os and os.path modules.
- The __file__ constant
- os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
- os.path.dirname(path) (returns "the directory name of pathname path")
- os.getcwd() (returns "a string representing the current working directory")
- os.chdir(path) ("change the current working directory to path")
Ref: https://bit.ly/3fy0R6m
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