﻿ 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:

``````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}
```

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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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