﻿ Python: Count of elements in each group from list based groups of elements - w3resource

# 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:

``````# Import the 'defaultdict' class from the 'collections' module.
from collections import defaultdict

# Define a function called 'count_by' that counts occurrences in a list based on a provided function.
def count_by(lst, fn=lambda x: x):
# Create a defaultdict to store the count of each value.
count = defaultdict(int)

# Iterate over the values in the list after applying the provided function.
for val in map(fn, lst):
# Increment the count for the current value.
count[val] += 1

# Convert the 'count' defaultdict into a regular dictionary and return it.
return dict(count)

# Import the 'floor' function from the 'math' module.
from math import floor

# Print the result of counting occurrences in a list of floating-point numbers using the 'floor' function.
print(count_by([6.1, 4.2, 6.3], floor))

# Print the result of counting occurrences in a list of strings using the 'len' function.
print(count_by(['one', 'two', 'three'], len))
```
```

Sample Output:

```{6: 2, 4: 1}
{3: 2, 5: 1}
```

Flowchart:

Python Code Editor:

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