Python: Count of elements in each group from list based groups of elements
Python List: Exercise - 216 with Solution
Write a Python program to group the elements of a list based on the given function and return the count of elements in each group.
- Use collections.defaultdict to initialize a dictionary.
- Use map() to map the values of the given list using the given function./li>
- Iterate over the map and increase the element count each time it occurs.
Sample Solution:
Python Code:
from collections import defaultdict
def count_by(lst, fn = lambda x: x):
count = defaultdict(int)
for val in map(fn, lst):
count[val] += 1
return dict(count)
from math import floor
print(count_by([6.1, 4.2, 6.3], floor))
print(count_by(['one', 'two', 'three'], len))
Sample Output:
{6: 2, 4: 1} {3: 2, 5: 1}
Flowchart:

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Previous: Write a Python program to merge two or more lists into a list of lists, combining elements from each of the input lists based on their positions.
Next: Write a Python program to split values into two groups, based on the result of the given filtering function.
What is the difficulty level of this exercise?
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Python: Tips of the Day
Given a predicate function, fn, and a prop string, this curried function will then take an object to inspect by calling the property and passing it to the predicate:
Example:
def tips_check_prop(fn, prop): return lambda obj: fn(obj[prop]) check_age = tips_check_prop(lambda x: x >= 25, 'age') user = {'name': 'Owen', 'age': 25} print(check_age(user))
Output:
True
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